Posts Tagged ‘minimum viable population’

Uncertain Future for the Gray Wolf

 

Again, An Uncertain Future for the Gray Wolf

By Ken Fischman, Ph.D.

August 23, 2012

 

It looks as though Interior Secretary Salazar has struck a deal with Wyoming to end its Endangered Species listing for wolves in that state. According to the New York Times, the arrangement will be similar to that now in force in Idaho and Montana, with a minimum number of 150 wolves and 15 breeding pairs. However, wolves will still be treated as vermin, to be shot on sight year round in 4/5s of the state. Thus, Wyoming has apparently received from the Obama administration most of what it had held out for.

The New York Times August 21, 2012 Editorial, “Uncertain Future for the Gray Wolf, “ (c f.) questioned whether 150 wolves/state would be a viable population for Wyoming, Montana, or Idaho. If you consider that my state, Idaho, contains about 1.3 million people, 20,000 black bears, and over 100,000 elk, the number 150 stands in stark contrast to these populations. No reputable biologist that I know of believes that such a number would be anything but a relict population, genetically threatened by inbreeding, and possibly extinction.

Even Ed Bangs, who was US Fish & Wildlife Wolf Recovery Coordinator, recently admitted that this number of wolves “is not defensible.”
Interestingly enough, the lead article in Science, September 2011, “Trophic Downgrading of Planet Earth”, emphasizes the value of wolves and other top predators in keeping a healthy balance in our ecosystems. It was authored by some of the world’s leading Conservation Biologists. The article is excerpted on the Ancient Pathways web site under the title of  “Trophic Downgrading or Where Have All the Predators Gone,?” and contains a lot of valuable information on the effect of apex predators.

Additionally, Times readers should know that the wolf hunting season in Idaho is now year around, if you count private land, which is about 40% of the state. Any land owner, with a valid wolf tag can shoot wolves on sight. When you consider that the southern third of the state is desert, in which wolves are rarely seen, the territory safe for wolves shrinks considerably more. Also, the number of wolves that can be killed in 8 out of 13 “Wolf Zones” is unlimited.

Obama promised that he would reverse the Bush administration’s politicization of science. This does not appear to be true for wolves. I guess that it is because they do not vote.

———————————————————————————————————————————————

New York Times

EDITORIAL

Uncertain Future for the Gray Wolf

Published: August 21, 2012

A Wolf Pack in Isle Royale NP

Wolves In Isle Royale National Park

Wolves in Montana and Idaho lost their endangered species status last year. Interior had concluded that both states had developed management plans that would keep wolf populations at healthy levels.

The delisting has led to the death of hundreds of wolves in sanctioned hunts. But at least Montana and Idaho established limits on hunting seasons and on the number of wolves that can be taken across the entire state. In Wyoming, by contrast, wolves in four-fifths of the state will be essentially treated as vermin that can be killed at any time, and for almost any reason.

Interior says not to worry. Most of Wyoming’s wolves are in the state’s northwest corner, it points out, and can be shot only during a defined hunting season. Further, the state has agreed not to reduce the statewide population below 150 wolves and 15 breeding pairs.

This is a more protective plan than Wyoming’s politicians, ranchers and hunters wanted a year ago. But whether it’s enough to guarantee a sustainable population is far from clear. Interior has promised to review its deals with Montana and Idaho after five years. It must demand the same of Wyoming. The question there is whether, after five years, there will be any wolves left to review.

 

 

The Case of the Missing Predator, or Please Pass the Shark Fin Soup

The Case of the Missing Predator, or Please Pass the Shark Fin Soup

THE PREDATOR/PREY RELATIONSHIP. WHY IS IT SO IMPORTANT?        

From time to time in this website, we examine important scientific papers in light of what they show us about subjects of interest to ourselves and our readers.

         The following paper (Crooks and Soule, Nature, 1999) has become a classic because it vividly shows how the presence or absence of a predator can have unexpected and important effects on an ecosystem.

(I regret that I cannot reprint the entire paper, and can show you only the abstract. Copywrite policies prevent me from doing so, even if I were to purchase it. This is detrimental to the free flow of scientific information, but I have no control over the situation.)


Mesopredator release and avifaunal extinctions in a fragmented system

Kevin R. Crooks1 & Michael E. Soulé2

  1. Department of Biology, University of California, Santa Cruz, California 95064, USA
  2. The Wildlands Project, PO Box 1302 2010, Hotchkiss, Colorado 81419, USA

Correspondence to: Kevin R. Crooks1 Correspondence and requests for materials should be addressed to K.R.C. 
(e-mail: Email: krcrooks@earthlink.net.).

Mammalian carnivores are particularly vulnerable to extinction in fragmented landscapes1, and their disappearance may lead to increased numbers of smaller carnivores that are principle predators of birds and other small vertebrates. Such 'mesopredator release'2 has been implicated in the decline and extinction of prey species2, 3, 4, 5, 6. Because experimental manipulation of carnivores is logistically, financially and ethically problematic6,7, however, few studies have evaluated how trophic cascades generated by the decline of dominant predators combine with other fragmentation effects to influence species diversity in terrestrial systems. Although the mesopredator release hypothesis has received only limited critical evaluation8 and remains controversial9, it has become the basis for conservation programmes justifying the protection of carnivores6. Here we describe a study that exploits spatial and temporal variation in the distribution and abundance of an apex predator, the coyote, in a landscape fragmented by development. It appears that the decline and disappearance of the coyote, in conjunction with the effects of habitat fragmentation, affect the distribution and abundance of smaller carnivores and the persistence of their avian prey.

Letters to Nature

Nature 400, 563-566 (5 August 1999) | doi:10.1038/23028; Received 22 February 1999; Accepted 5 July 1999


The Soule paper was a sort of scientific detective story.

Michael Soule, who is considered to be the dean of the field of Conservation Biology, if not its creator, examined a puzzling situation in his home city of San Diego, California. The city, although it is highly urban, is transected by many deep and mostly wild ravines that extend out to the ocean front. The ravines contain animal populations and are basically isolated from each other by houses, streets, etc. One can think of them therefore as islands of life, the denizens of which can enter and leave only with great difficulty.

When Soule surveyed the animal populations in these ravines, he noted a strange situation. In some of the ravines there were dense populations of song birds, whereas in others, there were hardly any at all.

The mystery was clarified when Soule examined the other animal populations in these “urban islands.” He found cats in some ravines, and coyotes in others, but never cats and coyotes together. He also noted that in those ravines where there were coyotes but no cats, there were plentiful populations of song birds, but in others where there were no coyotes, but many cats, song birds were missing.

This is partially a big fish, little fish story, with intriguing consequences and implications. The picture that Soule put together was the following: Coyotes and cats are both predators. We call coyotes mesopredators because they themselves are the prey of others, such as mountain lions and wolves. Coyotes, in turn prey on cats and cats eat birds as well as their eggs and young.  Did you ever think of your kitty as a predator when it brought a dead creature home? Well, domestic as well as feral cats are responsible for the deaths of millions of song birds every year!

In those ravines where the only predators were cats, the cats decimated the bird populations. However in those ravines where there were urban coyotes, they preyed on the cats, keeping their numbers way down, thus allowing the bird populations to flourish. Mystery solved.

So, what has this to do with our interests? Just this.  Wolves are keystone predators, meaning that they sit on top of the food chain (if humans are ignored), and due to this situation, their behavior and eating habits result in a cascade of effects to the rest of the ecosystem.

Yellowstone National Park, like those San Diego canyons, is a sort of island of wildlife, surrounded by ranches, highways, houses and other accoutrements of human habitation. Animals do not easily get in or out. When a few wolves were reintroduced there in 1995, some of the effects were anticipated, but others were not.

 The effects of these predators have been widespread and profound. First, they reduced the number of coyotes in the park considerably as the wolves took their place as the top predators in Yellowstone. Then they reduced the elk population from roughly 15-17 thousand to around 4,500 – 5,000 at present. Lest you think that this drop in elk population is the nightmare hunters fear it is in other locales, it all depends on whose ox is gored.

In fact, the elks, themselves an introduced species in the 1930s, had increased greatly in numbers, due mainly to the lack of predators. They overran and overgrazed the park, considerably  changing the ecosystem. How profound these effects were became apparent when the wolves reduced elk numbers and changed their behavior, by chasing them from the river bottoms into the hills.

Aspens, willows and other water–loving plants began to grow in riperian areas, resulting in the stabilization of crumbling creek banks and increasing the amount of shade. Cold water fish, like trout, returned to shaded, cooler waters. Other animal species also benefitted. Animals that depended on the availability of carrion left by the wolves, such as vultures, crows, and foxes made a strong comeback.

These changes have been examined in many studies of the Yellowstone ecosystem by Ripple as well as Creel, W.D. Smith, and Hebblewhite. The documentary film, Lords of Nature, dramatically shows the effects of these changes, both in Yellowstone and in Zion National Park, where extirpation of mountain lions in the main valley has resulted in its being highly degraded by the ever-increasing deer population. In side canyons, where mountain lions still live, the riperian plant and animal life remains lush.

In Yellowstone, the elk and wolves have alternated in population bursts. When wolf numbers increased, the elk numbers diminished. Then the wolf population, stressed by lack of prey, dropped in turn, enabling the elk to make a comeback. These cycles have been observed a number of times during the wolve's 16 year sojurne in Yellowstone, as the wolves and elk repeated their predator/prey dance.

In recent years, the roles of predators in keeping an equilibrium in other species have been intensively studied in many ecosystems. Their value more appreciated by biologists than by the general public. Who knew for example what profound effects the loss of sharks, who are top marine predators, would have on the world’s fisheries. Shark fin soup anybody?

Scientists debate number of wolves needed for species’ survival

 

Scientists debate ‘magic number’ of wolves needed for species' survival

[To my knowledge, this is the first article in the media to address from a scientific point of view the important issue of how many wolves are needed for a viable population. Chaney points out that according to the Conservation Biology 50/500 rule, from 2,000 - 5,000 wolves are needed in the Northern Rockies to insure a population with sufficient genetic diversity.

He also points out that the areas chosen for reintroduction, Idaho, Montana, and Wyoming, are artificial, ignoring the fact that wolves regularly move back and forth between these states and Canada. 

He looks at the much cited 1987 restoration goal of 150 wolves per state, and bluntly labels it as a dishonest political, and not a scientific number. Ed Bangs, the retiring Wolf Coordinator for USFW has admitted as much in a recent interview.

Finally, I would be remiss in not stating that Chaney's enlightening article appears to have come too late to save Northern Rockies wolves. As most readers know, they have been removed from the protection of the ESA. Idaho's and Wyoming's stated plans for them, will basically lead to either their total extermination or to their reduction to a few struggling packs and lone wolf wanderers, that will have little or no effect on the ecosystem and will be seldom even glimpsed in our forests.]

by Ken Fischman

By ROB CHANEY of the Missoulian | Posted: Sunday, May 22, 2011 7:00 am 

Conservation groups and the federal government continue to disagree how many gray wolves are needed in the Northern Rockies to ensure the species’ survival. National Park Service photo

One of the biggest arguments left unresolved by last year's wolf lawsuit was the most obvious: How many wolves are enough?

The U.S. Fish and Wildlife Service took the gray wolf off the endangered species list in 2009, with the caveat that at least 150 wolves and 15 breeding pairs endure in each of the three states in the northern Rocky Mountain population (Montana, Idaho and Wyoming).

Recent surveys found at least 1,700 wolves in that area – more than enough to justify delisting.

But a coalition of environmental groups sued the government, claiming those numbers were wrong. To survive and thrive, they argued, the population needed at least 2,000 and preferably 5,000 wolves.

FWS biologists said they used the best available science to pick their number. Coalition members cited the well-established rules of conservation biology to justify their threshold. While the scientists dueled, U.S. District Judge Donald Molloy decided the case on a technicality and Congress reversed him with a budget rider. Wolves in the Northern Rockies are now delisted, but almost nobody's happy.

*****

Over the past decade, biologists have sought a "magic number" that would simplify endangered species debates. In 2010, an Australian team led by Lochran Traill of the University of Adelaide published a study declaring 5,000 was the population size required to prevent any species' extinction.

"We don't have the time and resources to attend to finding thresholds for all threatened species," Traill told Science Observer Magazine. "(T)hus the need for a generalization that can be implemented across taxa (classes of animals and plants) to prevent extinction."

But another group of U.S. Forest Service researchers along with American and British professors warn that a simple tool may be a flawed tool. While they agree that an easily understood standard helps persuade judges or members of Congress of the need for action, the 5,000 figure doesn't add up. Their paper will be published in the journal Trends in Ecology and Evolution.

"It's natural for any policy maker and practitioner to look for ways of simplifying the overwhelming process of endangered species management," said Greg Hayward of the Forest Service's Alaska Region Office. "If that worked, it would be a delightful world to live in. But if you're really going to do anything positive, in terms of turning around the situation for these species, going for that simple rule of thumb isn't going to help."

Both sides use a lot of math to make their points. Traill and company looked at 1,198 species with a computer model that calculated how many of each would be needed for the plant or animal to survive in the long term. In particular, the study looked at how many are needed to ensure a species doesn't in-breed itself into extinction.

That's key because one requirement to getting off the endangered species list is a population big enough to guarantee genetic diversity. Earthjustice attorney Doug Honnold relied on that in his argument to Molloy, to show why the wolf should remain a listed species.

"If you're talking about genetics, then there are some basic genetic principles that apply across all species," Honnold said. "It's been documented with every species that's been studied."

Honnold referred to what's called the "50-500 rule" which states you need at least 50 breeding-age females of a species for short-term survival or 500 for the long term. In the case of wolves, there's usually only one breeding female in a pack of four to 10 wolves, so the total population number balloons to 2,000-5,000.

*****

The "magic number opponents" respond that genetics isn't everything. In the case of wolves, where might that 2,000-5,000 figure apply? Do we need a minimum viable population in the three states where wolves were reintroduced back in 1995? Or should the figure be spread across the six-state area now delisted by congressional fiat (adding Utah, Washington and Oregon to Montana, Idaho and Wyoming)? Does it count the Canadian wolves that have relations with American packs along the international border?

"Under the Endangered Species Act, we sort of ignore other segments of populations that are outside the United States," said Hayward's colleague, Steven Beissinger of the University of California-Berkeley. "In the case of the paper we did, one thing we found was, the particular technique people used to come up with this minimum number was very context-specific."

In other words, each animal needs its own formula. Passenger pigeons had different lifespans and breeding rates than wolves. They could fly across continents at will, while wolves may be stymied by freeways. Passenger pigeons were, in fact, the most abundant land bird in the continental United States – 3 billion to 5 billion individuals – before the population crashed between 1870 and 1890. [ note: Here I disagree with the reporter. The passenger pigeon population did not crash. It was deliberately exterminated, using the most atrocious means imaginable.]

Science rarely gets to be just science. Lots of scientific reasons justify the wolf's presence on the landscape: It reduces elk populations, which in turn improves the plant communities along streams, which brings back songbirds and beavers.

But reduced elk numbers aggravate a hunting community that's invested millions of dollars to improve elk habitat. Wolves also have proved a poster target for politicians who want to leash the Endangered Species Act.

Natural Resources Defense Council staff scientist Sylvia Fallon said the U.S. Fish and Wildlife Service knew it would face public resistance if it proposed reintroducing lots of wolves, so it picked a deliberately low 150-per-state figure to get the reintroduction in play.

"They (FWS biologists) say they came up with that number in consultation with scientists, but they never said who they were," Fallon said. "It was some guesswork factoring in social and political considerations at the time, what would be acceptable to the states and the public."

FWS attorneys rejected that claim in their court briefs, but they never got to have the argument in Molloy's courtroom. Without ever discussing what an appropriate number should be, the judge only said the federal government illegally used state boundaries to divide a natural population.

*****

Beissinger suggested a better target in the search for the elusive magic number. Instead of a unified field theory of how many of a species is needed to survive, we humans should settle on what risk factor we're willing to work with, he said.

"In my profession, we don't have a single standard that's been set for what degree of risk we're willing to accept for a species to go extinct," he said. "I could make a calculation for a species and say nine times out of 10, it would be viable there, for 50 years. Would that be good enough, or would you want a 95 percent chance, or an 80 percent chance? But it's too naive to use just measures of population size and come up with some rule of thumb whether a population is safe or not."

Reporter Rob Chaney can be reached at 523-5382 or at rchaney@missoulian.com.

Note: some passages were bolded by KF for emphasis

 

The Number of Wolves Needed for Survival

 

 

There has been a swirl of recent events, which threatens the very survival of wolves in the northern Rockies. First, there was the delisting of wolves from the ESA, then the declaration by IDF&G that there will be no kill quota in most of the state during the upcoming wolf hunt, and IDF&G's target of killing 60 out of the estimated 80 wolves in the Lolo region of the Clearwater NF, for allegedly lowering the numbers of elk there. 

Right from the beginning of wolf reintroduction, there has been controversy over the numbers of wolves that would indicate that they were biologically and genetically recovered. Much of the numbers thrown around were quite frankly politically derived and not scientific.

The following article is as far as I know, the first serious attempt by a reporter to examine this issue in an objective way. For that reason, it is well worth reading, if only to compare it with the nonsensical and often irrational opinions that have appeared in much of the western states media.

Ken Fischman

 

 

Scientists debate ‘magic number’ of wolves needed for species' survival

 

By ROB CHANEY of the Missoulian | Posted: Sunday, May 22, 2011 7:00 am |

 

Conservation groups and the federal government continue to disagree how many gray wolves are needed in the Northern Rockies to ensure the species’ survival. 

One of the biggest arguments left unresolved by last year's wolf lawsuit was the most obvious: How many wolves are enough?

The U.S. Fish and Wildlife Service took the gray wolf off the endangered species list in 2009, with the caveat that at least 150 wolves and 15 breeding pairs endure in each of the three states in the northern Rocky Mountain population (Montana, Idaho and Wyoming).

Recent surveys found at least 1,700 wolves in that area – more than enough to justify delisting.

But a coalition of environmental groups sued the government, claiming those numbers were wrong. To survive and thrive, they argued, the population needed at least 2,000 and preferably 5,000 wolves.

FWS biologists said they used the best available science to pick their number. Coalition members cited the well-established rules of conservation biology to justify their threshold. While the scientists dueled, U.S. District Judge Donald Molloy decided the case on a technicality and Congress reversed him with a budget rider. Wolves in the Northern Rockies are now delisted, but almost nobody's happy.

*****

Over the past decade, biologists have sought a "magic number" that would simplify endangered species debates. In 2010, an Australian team led by Lochran Traill of the University of Adelaide published a study declaring 5,000 was the population size required to prevent any species' extinction.

"We don't have the time and resources to attend to finding thresholds for all threatened species," Traill told Science Observer Magazine. "(T)hus the need for a generalization that can be implemented across taxa (classes of animals and plants) to prevent extinction."

But another group of U.S. Forest Service researchers along with American and British professors warn that a simple tool may be a flawed tool. While they agree that an easily understood standard helps persuade judges or members of Congress of the need for action, the 5,000 figure doesn't add up. Their paper will be published in the journal Trends in Ecology and Evolution.

"It's natural for any policy maker and practitioner to look for ways of simplifying the overwhelming process of endangered species management," said Greg Hayward of the Forest Service's Alaska Region Office. "If that worked, it would be a delightful world to live in. But if you're really going to do anything positive, in terms of turning around the situation for these species, going for that simple rule of thumb isn't going to help."

Both sides use a lot of math to make their points. Traill and company looked at 1,198 species with a computer model that calculated how many of each would be needed for the plant or animal to survive in the long term. In particular, the study looked at how many are needed to ensure a species doesn't in-breed itself into extinction.

That's key because one requirement to getting off the endangered species list is a population big enough to guarantee genetic diversity. Earthjustice attorney Doug Honnold relied on that in his argument to Molloy, to show why the wolf should remain a listed species.

"If you're talking about genetics, then there are some basic genetic principles that apply across all species," Honnold said. "It's been documented with every species that's been studied."

Honnold referred to what's called the "50-500 rule" which states you need at least 50 breeding-age females of a species for short-term survival or 500 for the long term. In the case of wolves, there's usually only one breeding female in a pack of four to 10 wolves, so the total population number balloons to 2,000-5,000.

*****

The "magic number opponents" respond that genetics isn't everything. In the case of wolves, where might that 2,000-5,000 figure apply? Do we need a minimum viable population in the three states where wolves were reintroduced back in 1995? Or should the figure be spread across the six-state area now delisted by congressional fiat (adding Utah, Washington and Oregon to Montana, Idaho and Wyoming)? Does it count the Canadian wolves that have relations with American packs along the international border?

"Under the Endangered Species Act, we sort of ignore other segments of populations that are outside the United States," said Hayward's colleague, Steven Beissinger of the University of California-Berkeley. "In the case of the paper we did, one thing we found was, the particular technique people used to come up with this minimum number was very context-specific."

In other words, each animal needs its own formula. Passenger pigeons had different lifespans and breeding rates than wolves. They could fly across continents at will, while wolves may be stymied by freeways. Passenger pigeons were, in fact, the most abundant land bird in the continental United States – 3 billion to 5 billion individuals – before the population crashed between 1870 and 1890. [ note: Here I disagree with the reporter. The passenger pigeon population did not crash. It was deliberately exterminated, using the most atrocious means imaginable.]

Science rarely gets to be just science. Lots of scientific reasons justify the wolf's presence on the landscape: It reduces elk populations, which in turn improves the plant communities along streams, which brings back songbirds and beavers.

But reduced elk numbers aggravate a hunting community that's invested millions of dollars to improve elk habitat. Wolves also have proved a poster target for politicians who want to leash the Endangered Species Act.

Natural Resources Defense Council staff scientist Sylvia Fallon said the U.S. Fish and Wildlife Service knew it would face public resistance if it proposed reintroducing lots of wolves, so it picked a deliberately low 150-per-state figure to get the reintroduction in play.

"They (FWS biologists) say they came up with that number in consultation with scientists, but they never said who they were," Fallon said. "It was some guesswork factoring in social and political considerations at the time, what would be acceptable to the states and the public."

FWS attorneys rejected that claim in their court briefs, but they never got to have the argument in Molloy's courtroom. Without ever discussing what an appropriate number should be, the judge only said the federal government illegally used state boundaries to divide a natural population.

*****

Beissinger suggested a better target in the search for the elusive magic number. Instead of a unified field theory of how many of a species is needed to survive, we humans should settle on what risk factor we're willing to work with, he said.

"In my profession, we don't have a single standard that's been set for what degree of risk we're willing to accept for a species to go extinct," he said. "I could make a calculation for a species and say nine times out of 10, it would be viable there, for 50 years. Would that be good enough, or would you want a 95 percent chance, or an 80 percent chance? But it's too naive to use just measures of population size and come up with some rule of thumb whether a population is safe or not."

Reporter Rob Chaney can be reached at 523-5382 or at rchaney@missoulian.com.

 

Biogeographic And Genetic Factors In Northern Rockies Wolf Populations

 

       Biogeographic and Genetic Factors in Northern Rockies Wolf Populations

Ken Fischman, Ph.D.(Genetics)   April 9, 2008

 

         As we all know, Fish & Wildlife (USFW) has proposed delisting the wolf populations of Idaho, Montana, and Wyoming. They have recently estimated total wolf populations in these three states to be 1,242, with 92 breeding pairs.  Wolf population in Idaho is currently estimated at 672 ( Nadeau et al., 2007), with 42 breeding pairs (Bangs, Personal Communication, 3/8/07).

         Idaho Fish & Game proposes maintaining a minimum of 100 wolves in their state, with a minimum of 15 breeding pairs (IDFG, 10/07). 

         This paper examines these two population targets, some recent thinking about the genetics and biology of wild animal species, and finally the possible biogeographic and genetic consequences of the minimum number of wolves projected by the Idaho authorities.

          First, let’s look at the effects of population size on the viability of a species. The Hardy-Weinberg Principle states that allele frequencies (that is different forms of a gene) will not vary over time in a population. However, this principle only holds for a population sufficiently large to overcome the tendency for Genetic Drift to change gene frequencies. 

         Genetic Drift refers to the tendency for genes to become more common or more rare in successive generations.  It has no preferred direction, and it tends to sweep genetic variants out of the population with time.  It thus opposes Mutation, which introduces novel variants into the population, thus increasing species resiliency.  i.e. the ability to resist demographic shocks and adapt to changed conditions.

         Small populations often show a Founder Effect, in which one or more gene variants increasingly predominate as inbreeding increases. Inbreeding Depression, results from an increase in homozygosity. That is the state in which there are two identical copies of genes.  Homozygosity increases the possibility of recessive alleles expressing themselves. Some of these will turn out to be valuable, but most will be deleterious, thus weakening the genetic fitness of the population.

         Wolf packs, due to their size, and if they are effectively isolated from other wolf populations, also may show a Founder Effect, thus adversely effecting the long-term survival of the population. The increase in homozygosity would in turn be responsible for high frequencies inherited diseases.  This is something that wolf biologists should be on the watch for.

          What counts in small populations is not their census size, but the Effective Population size or number of breeding individuals in the population. The literature on wolves indicates that most packs have only two Effective Breeders.  However, the latest data on Yellowstone packs show multiple breeders within some packs (Smith, 2006).  I am curious as to whether this is also true for other northern Rockies wolf populations.  On the other hand, can this situation be attributed to something unique about Yellowstone wolves, such as access to large prey populations or lack of stress?  An answer to this question would be important for calculating viable population numbers.

         Let’s examine some of the other possible consequences of small population size.  Small populations in particular are prone to large fluctuations in size. Therefore, it is important to consider this in some detail.  Why does this occur?

           Inbreeding is one source of changes in population size.  The smaller the population, the more likely it is that related individuals will breed with each other, and their offspring will have a far higher number of homozygous genes.

         That is hard to detect, but its consequences, although sometimes subtle, can be severe.  Michael Soule showed that inbreeding of Poland Swine lead to deleterious effects in as soon as the second generation.  The inbreeding resulted in decrease in piglets/litter, decreased survival of newborns, and skewed sex ratios.  As we shall see, this last may be of particular importance for wolves.

         As I previously stated, inbreeding leads to lack of genetic diversity, which in turn may result in inability to adapt and evolve under changing conditions.

         There are also Demographic effects.  One such effect would be fluctuations in the size of small populations. Another is possibility of imbalance of sexes, and increasing chances of a same sex generation. For example, 3 offspring’s chance of being the same sex is 0.25 or 1/4.  If a population remains at a low level for several generations, then a same sex generation becomes almost inevitable.

         Here is an example of a problem resulting from such a situation. One of the last populations of Kakapo, an extremely rare, flightless parrot, was found on an island off the coast of New Zealand.  There were 18 of them. Unfortunately, they were all male.

         A small population is also susceptible to  Environmental effects, such as forest fires, disease, climate change, etc

         Anthropogenic effects loom large for small populations.  These are events such as: accidents, hunting, killing of so-called problem Wolves, and illegal takings. This last is of particular importance in Idaho.  Since wolf reintroduction, 59 cases of illegal hunting/killing have been documented by ID F&G.  Due to its furtive nature, this is probably only a portion of such deaths. 

         Also, last year, 45 Wolves were deliberately killed by ID F&G, USFW, and ranchers. These deaths add up to more than 6% of the Idaho Wolf population.

         All of these effects contribute to population decrease, both directly and indirectly by damaging the social structure of a pack.  Most anthropogenic effects are indiscriminate acts with unforeseen consequences.  For instance one of the pack members killed might be the Alpha female.

         There are of course important Genetic consequences, resulting from the decreases in population size brought about by these demographic, environmental, and anthropogenic effects. As previously stated, inbreeding and small population size will increase the degree of Homozygosity. Recessive genes only express themselves when there is a double dose of them. And, because most harmful genes are recessive, this will result in a larger number of unfit animals and a greater number of deaths.

         Homozygosity also results in an increase of Monomorphisms and an associated  decrease of Polymorphisms, which are multiple functional alleles in a population. This can be damaging, especially if genes effecting the Immune system are involved.  The situation can also lead to a continuous and therefore increasing fixation of deleterious genes. We give this the fanciful name of “Muller’s Ratchet,” which is the continual loss of individuals with the smallest number of deleterious genes because there are so few such individuals.  Due to the elimination of these individuals, generation by generation, the population’s genetic load of damaging genes increases, thus decreasing its adaptive fitness, and leading to its eventual extinction.

         As the expression of recessive alleles become more common due to increase in homozygosity, a species becomes less fit because they are less diverse and therefore more subject to mass die-offs due to disease, etc.  Heterozygosity, in contrast, is increased by outbreeding, leading to improved adaptive fitness of the animals.                

          I would like to put the 673 wolves in Idaho in demographic and geographical perspective.  The size of Idaho is 82,751 square miles. That works out as one wolf for every 123 square miles.  The Human population is more than 1,240,000, which means one wolf for every 1,842 people.

         The chief prey of Idaho wolves are Elk. Their 2006 numbers were estimated  by IDFG as 102,706. The Wolf population of Idaho is actually very small in comparison.  There are 153 Elk for every wolf. 

         Geneticists and Biogeographers find it useful to employ the term Minimum Viable Population or MVP.  This is defined as the smallest population size likely to persist indefinitely in a particular area.

         Here is a little history lesson.  Main and Yadov(1971) examined marsupial populations on several Australian offshore islands and came to the conclusion that a minimum of 200 – 300 animals was necessary to maintain those populations.  However, they also concluded that MVP differs from one species to another, and according to conditions.

          Conservation Geneticists usually consider that a population of less than 500 individuals is endangered, Keep in mind however, that what is important to species preservation is not total population, but the number of Effective Breeders, and many Conservation geneticists recommend a minimum of 50  breeder pairs.

          If we assume an average of ten wolves/pack, with one breeding pair, this would extrapolate to a population of 500 wolves.

         It is of course self-evident that larger populations are usually safer for the viability of a species or sub-population of a species. The key question remains as to what is the minimum number of individuals that would put a population at risk of extinction. 

         All of the factors I have previously mentioned are involved in such a determination, but perhaps another factor is more important in this situation. That is whether or not there is such a thing as a megapopulation of wolves in the northern Rockies.

         USFW speaks of a northern Rocky wolf megapopulation, connected by wolves dispersing from packs.  The megapopulation they describe extends from Canada, western Wyoming and Montana to central Idaho, and from there to northern Utah, a distance of approximately 800 miles.

         Such a connection is particularly problematical between central Idaho and Northern Utah, yet the US FW has conflated what appear to be two distinct areas. I do not know of any data that supports this idea. Lets examine the evidence for the existence of such corridors:

         Since wolf reintroduction, and through the winter of 2006, eight wolves traversed between northwest Montana and central Idaho. Of those, only three have successfully bred. Attempts made by wolves to move between the central Idaho and Yellowstone populations have fared even worse. Only one wolf completed the journey in eleven years since reintroduction (Robinson, 2006)

         These numbers of dispersing wolves are so small that they are likely to have little or no effect on gene flow between these populations.  Additionally, the fact that in such a long time, span, only three of the nine dispersing wolves bred, makes it likely that a larger number of wolves would be necessary if their movement between these regions could be successfully translated into significant gene pool effects.

         To settle the question as to whether these so-called corridors have a real effect, it would be best to do comparative genetics studies between populations rather than to continue to track lone wolves.        

         Much has been made of the rapid increase in wolf numbers since the initiation of wolf recovery in the 1990s. This increase has been cited by the USFW as a sufficient reason to remove them from the Endangered Species list.

         Is this population increase truly remarkable, or is it due to the rapid filling of an ecological niche for a keystone predator that had been nearly empty for well over a century?  Only time will tell, but I suspect that as these niches fill, rates of increase in wolf population will slow down. This is especially liable to occur because many of the conditions that led to wolf extinction in the lower 48 in the first place, are recurring. Hunting, culling of so-called problem wolves, and illegal takings may result in destruction of the intricate social fabric of wolf packs, putting them at an even greater risk of a second extinction.  Just the other day, someone in eastern Idaho shot two wolves because they “were near his ranch.”  (KPBX radio, 4/3/08).

         It is a frequent mistake to assume that current trends will persist indefinitely into the future.  To assume that wolf populations will continue to increase at present rates is as biologically naive as were the assumptions of homeowners and Wall Street investors who have lately discovered that ever-increasing housing values are an illusion.  No one escapes the laws of Nature indefinitely.

                  So we turn to the key question of what is the Minimum Viable Population for Canis lupis?  It is important to realize that MVP has two corollaries, having to do with population size and time: (1) The smaller the population, the more likely it will go extinct within a certain time period.  (2) The longer the time period, the more likely extinction is for a population of any size.

         Mark Shaffer, in his studies of Grizzly populations in national parks, suggested that a 95% chance of persistence for 100 years would be a reasonable goal.

         Conservation Geneticists have recently set more stringent parameters of a 99% chance of persistence for 1,000 years.

         In reality, viability is too complex an issue to be reduced to a single number.  A population of some specified size might be viable under one set of circumstances, but not under another set, or viable for one species, but not for another.

         Soule and Gilpin (1987) came to the conclusion that theoretical numbers cannot be relied on, only real data, analyzed in complex ways and checked against real-life situations can be relied upon.  They called this method Population Viability Analysis (PVA).

         So, how large a population is sufficient to insure viability?  Soule stated that arguing from theory, several lines of analysis produce estimates of several thousand or larger. He said “ I am assuming a 95% expectation of persistence, without loss of fitness, for several centuries.  My guess is that it would be in the low thousands.  …estimates below this range should be an automatic signal for scrutiny.” (Soule. 1987)

         However he leaves us with the following warning:  “…anyone who applies the few thousand estimate to a given species, citing this author as an authority, deserves all the contempt that will be heaped on him or her.”

Considering all the evidence accumulated, it is clear that the wolf management plans of the federal and state agencies are not based on sound scientific and genetic data or theory.  If they are carried out as presently planned, they will undoubtedly lead to genetic impoverishment and possibly to a second extinction of wolves in the Rocky Mountain region.

Delisting isn’t based on sound science

 

April 15, 2009

Idaho Statesman

Delisting isn’t based on sound science

BY KEN FISCHMAN, Ph.D. AND NANCY GILLIAM, Ph.D. 

Secretary of the Interior Ken Salazar recently ruled that wolves be removed from the Endangered Species Act protected list.

We do not understand how he could have given this complex issue the thorough review it deserved in six weeks. Sadly, we suspect that this is yet another in a long history of political decisions about wolves, and not the scientific one that we had hoped for from this new administration.

The U.S. Fish and Wildlife Service claims that the wolves have made a significant comeback, and that a population of 1,500 wolves in Idaho, Wyoming and Montana will ensure their continued viability. Their number is not a biological reality, but a bureaucratic concept. In reality, there are three distinct populations, each numbering in the hundreds.

Ed Bangs, the wildlife service wolf coordinator, claimed that he had new evidence of genetic connection between distant wolf populations because, in 11 years, a few wolves have wandered between Yellowstone and Central Idaho. What counts biologically is not that a few lone wolves have made long journeys, but whether they have contributed genes to the other populations.

Bridgett vonHoldt from UCLA and her colleagues, in their recent study of the genetics of 500 wolves, has demonstrated that there is no gene flow between these three geographically distinct populations.

Scientists tell us that by 2050, from one third to one half of all species will go extinct due to climate change and habitat loss. Those already on the brink are likely to disappear first.

The low number of wolves living in the Rockies now leaves them vulnerable to inbreeding and environmental challenges.

With populations segregated, predicted habitat changes from warming temperatures are a further threat. We already are seeing habitat loss because of increased acreage burned in forest fires, increased tree mortality caused by disease and increased severe weather patterns.

The principles of conservation biology, the science that deals with extinction and viability of wild animals, also indicate that present numbers of wolves in the Rockies are too low. Michael Soule, the dean of conservation biology, has estimated that biologically viable populations would be “several thousand or larger.”

Our point is not that the wolves should never be delisted, but that doing so at this time would be premature. In a manner of speaking, the wolves are not yet out of the woods.

We do not have to guess at the consequences of premature delisting. In January, when the Bush administration attempted to delist wolves, they were left unprotected for three months until a federal judge issued an injunction. During that time, 132 wolves were killed. At that rate, the entire Northern Rockies wolf population could go extinct in three years.

The big, unanswered questions are what is the minimum biologically viable population for wolves, and how many wolves are necessary to ensure gene flow between the various populations and to avoid the consequences of inbreeding, such as loss of vigor, birth defects and decreased survivability of pups.

President Obama has been promising us a science-based approach to such issues. In fact, the president stated recently during his stem-cell research signing, “É We make scientific decisions based on facts, not ideology.” This is what we would like to happen with respect to wolves.

We were signatories of a letter to Salazar from Northern Rockies groups urging him to convene an expert panel of non-governmental scientists, who would examine the wolf issues.

Wolves have been a matter of bitter contention in the West. Science-based conclusions of a panel of experts may offer a way out of this dilemma, if both sides could be persuaded to accept its conclusions. If the Salazar decision is left to stand, it is certain that these issues will be dragged into court again.

Ken Fischman is spokesman for the Northern Rockies Wolf Group and Nancy Gilliam is director, Model Forest Policy Program. Both are from Sandpoint.