Transcript Case Studies II

Wolves
•Wolves are endangered or extirpated in many parts of their
(former) range.
•The gray wolf, Canis lupus, had a range in North America
from the arctic to central Mexico.
•In the old world, gray wolves ranged from arctic Siberia
and Scandinavia to the deserts of Israel, and were once
common in the forests of Europe.
•Also in the old world, most populations outside of northern
China and Siberia are small and isolated.
A little basic wolf biology
• Wolves are social animals, usually grouped in packs,
which consist of a set of behaviourally dominant parents
(the s), their offspring of the last few years, and other
non-breeding adults, which have been accepted into the
pack, but are unrelated.
• Bond between paired dominant animals may be for life
• The age of first reproduction is generally about 2-3 years.
The average litter is about 6 pups.
• Pups are weaned between 2 - 3 months.
• By 7-8 months they hunt with their parents
• At 1-2 years, males may leave their pack and attempt to
form a new one on their own, or they may remain with
their family pack
• Males are the ones forming packs, but they may take
females with them.
• Wolf packs have established territories. The size varies
from about 128 to 2560 km2.
• Wolves may move up to 50 km in a day.
• They establish the boundaries of territories by scent
marking.
• Other pack(s) may temporarily use a portion of competitor
pack’s territory
• Wolf packs establish their presence even without recent
marking by howling at night. Howling may also locate other
members of the pack temporarily separated, sound an
alarm etc.
• Other predatory species are supported by wolf kills,
including ravens, foxes, vultures, wolverines and eagles.
Recent population estimates:
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520 in Michigan
537 in Wisconsin
1600 in Montana, Idaho, Wyoming
5900-7200 in Alaska
6300 in 1980 in British Columbia
4000-5000 in Alberta
For the U.S. these recent estimates contrast with the lows
reached during the 1950s, when the total population of grey
wolves had declined to <1000 occupying <1% of its historic
range.
• 2900 in northern Minnesota
•this population has grown so much it was removed from
Endangered Species Act protection in March 2009
Recent information (Coastal wolves are 'like no other
wolves': study By Judith Lavoie, Canwest News Service
March 12, 2009) suggests these are not all one genetic
population (i.e. grey wolves).
• The wolves of the west coast (California north to coastal
Alaska) have reddish-brown fur, feed on marine resources
including seals, salmon and appear to be genetically and
evolutionarily distinct from other, contiguous gray wolf
populations.
• It is now suggested they may be deserving of separate
protection, even while gray wolf populations have grown and
been taken off endangered species lists.
Some specific examples of wolf populations and their
conservation…
The Wolves of Isle Royale
Isle Royale is an American National Park located only about 30
km from the Canadian coastline in Lake Superior. The total
area of the main island and a few small surrounding islands
which are also part of the park is 540 km2.
• Moose arrived on Isle Royale, crossing a winter ice bridge
from Canada, before 1910. With no predators, moose
increased to high density, then had large amplitude
fluctuations in population size into the 1940s. Peak numbers
exceeded 2000 moose in the late 1920s, after the island was
made a sanctuary in 1925.
• The cycles were probably due to starvation.
• In 1949, wolves crossed a temporary ice bridge onto Isle
Royale, and have lived there ever since.
• Studies of this isolated predator-prey system began in 1953
• Fascinating system since: 1) little or no immigration or
emigration; 2) no hunting by humans; 3) little human
disruption (e.g. introduced dog diseases); 4) simple
ecosystem; 5) confined quarters focuses biological
interactions
From early measurements of wolf and moose numbers,
moose reproductive rates, and wolf kill rates, L.D. Mech
believed that wolves regulated the moose population near an
equilibrium value. He thought predator-prey cycles would get
‘tighter and tighter’.
• A study of the ages of moose kills over a number of years on
Isle Royale indicated that wolves took principally calves and
older animals, i.e. moose with the lowest reproductive values.
• Only during the late 1970s, when moose numbers were low
and wolf numbers had increased with pack separation, were
any significant number of moose of
1959
ages 3-7, the prime reproductive
ages, killed. This suggests that wolf
kills are not likely to be sufficient to
regulate moose numbers.
0
10 20
1985
Age Class (Moose)
wolf kill highest when
moose abundant,
lowest when moose
numbers were low
• Moose numbers peaked at >1500 in the 1970s, declined during
the early 1980s, and increased during the early 1990s, before
crashing (80% mortality) due to starvation in 1996 (Peterson
1999).
• Wolf population size has not followed moose numbers.
• Moose density appears to be governed by their relationship
with plant food and less by wolf-driven mortality.
• Moose also are affected by parasites (ticks), which build up
large populations during warm summers and winters
• Ticks reduce moose vigour, leaving them exposed to more wolf
predation. During 2003, the moose population fell dramatically,
apparently in response to climate-change induced parasitism
by ticks and resulting exposure to wolf predation.
• Most recent numbers (2007): 30 wolves, 490 moose
• Winter severity and tick infestation were both regarded as
important in recent year declines in the moose population.
recent population data
typically 3 wolf
packs, though they
vary in number and
size of territory
through time
see more at: http://www.isleroyalewolf.org/wolfhome/home.html
Population Control and the wolves of the Yukon
• The Yukon government had a 5-year program of controlling wolf
numbers by hunting, trapping and poisoning. The reasons are
economic. Hunting of elk and caribou produces a tourism
industry of significant value to the territory. As well, there are
demands from native communities that the abundance of large
game animal prey be maintained or increased to meet the
needs of hunters.
• However, other predators contribute significantly to the problem,
e.g. both grizzly and black bears.
• The government reduce wolf populations in an area called the
Aishihik region around Kluane National Park.
• In this region, both caribou and moose populations have
declined and continue to decline even after closing the caribou
hunt and greatly reduced moose harvest.
• Even the government admits that the yields of moose and
caribou over the last decade were not sustainable.
•Renewable Resource officials
admit that there is good
evidence from elsewhere that
the wolf population will decline
as resources become scarce,
yet they argue that the long
recovery period for caribou
necessary (a 'predator pit') with
limited wolf control would be
unacceptable to their client
groups.
• Hayes et al. (2003) reported that moose and caribou both responded
favourably in terms of survival and recruitment in areas where wolves
were controlled and that wolf predation was responsible for low
moose numbers
• They further recommended that the government (of which they are
employees) limit human hunting to 2 and 5% for caribou and moose,
respectively, and that wolf control continue
Reintroduction of wolves to Yellowstone National Park
• Reintroduction of species into their native habitats is
desirable to return ecosystems to a more natural state. The
success of reintroduction depends on establishing sufficient
genetic variability and in reaching a minimum viable
population size.
• Wolves were directly and intentionally extirpated from the
park in 1930. They were thought to pose a threat to the herds
of deer, elk and other game animals populating the park.
• Is the area into which animals are reintroduced large enough
to maintain a minimum viable population?
• For wolves this is a severe problem. The natural density for
wolves is about 1 mature animal per 26 km2 (e.g. Frankel
and Soule 1981).
• Considering social structure, it was estimated that a
minimum area of between 39,000 and 78,000 km2 was
needed. However, Yellowstone, the largest park outside the
arctic in North America, has a total area of only 9000 km2.
• One of the ecologically important arguments for its
reintroduction is that it is the largest missing mammal from the
pre-development Yellowstone ecosystem.
• Wolves were thought to be necessary to restore ecological
balance and prevent overgrazers by elk, moose, deer.
• Arguments against reintroduction generally come from
ranchers in the area (Montana, Wyoming, and Idaho), who
believe that wolves will inevitably prey on livestock.
• The reintroduced wolves were designated a "non-essential
experimental population". According to the Endangered
Species Act, wolves were full protected within the park and
reintroduction area, but ranchers had the right to kill any wolf
which endangered livestock. Funds were privately collected to
reimburse ranchers for any livestock proven to be killed by
reintroduced wolves.
• Reintroduction began in 1995 with 14 animals from British
Columbia, followed by 17 more in 1996. Reproduction
resulted in a total of 21.
• By the end of 1996 there were 51 wolves.
• In 2003 there were 59 pups and 115 adults
or 174 animals.
• Population delisted in 2009, and hunting
was allowed in some states (e.g. Idaho,
Montana, Wyoming). It is now a “experimental,
non-essential population”. The population is protected within
Yellowstone, but not outside, where a limited hunt is
permitted.
• The regional population is called the “Northern Rocky
Mountains Distinct Population Segment”
• total number (2009) was 1600 in Montana, Idaho and
Wyoming, encompassing 95 breeding pairs
The most recent update on Yellowstone wolves shows the
population numbers since the beginning of re-introduction:
And the number of pups surviving each year since
reintroduction:
Why was this reintroduction so important?
• Without the top predator, a trophic cascade occurred.
• Populations of elk browse and damage their favorite food,
quaking aspen (Populus tremuloides).
• Initial studies of this cascade (Ripple et al. 2001) indicate that
it may well not be wolf predation on elk that affects aspen,
rather it is different use of habitats by elk to avoid predation
risk that releases some aspen from browsing damage.
• The root suckers (quaking aspen reproduces more asexually
than by seed) grow taller in areas used more heavily by the
wolf packs in Yellowstone than in areas little used by wolves
(and therefore used more heavily by elk).
• The last of the original wolves introduced to Yellowstone
died in early 2003, but the introduction effort has been such
extremely successful.
• Yellowstone is not the only site of wolf reintroduction. Wolves
have been reintroduced to a number of other sites in the
northwestern and southwestern regions of the U.S.
• In almost every area the same objections from ranchers
have occurred. The ‘non-essential’ designation and
reimbursement for loss has made most reintroductions
successful.
Red Wolf
• The red wolf (Canis rufus) once roamed the southeastern
US in forests and coastal marshes. It ranged inland to
central Texas, Missouri and southern Illinois.
• Ecological extinction of the red wolf over most of its habitat
in the U.S. occurred during the 1970s due to human
encroachment and development over much of its habitat.
• The last remaining wild red wolves live in coastal marshes in
the southeast along the Atlantic coast.
• extinct in wild by 1980
• The US Fish and Wildlife Service began a captive breeding
program in 1973 (14 animals used), with
40 different facilities participating today
• As of 1990 there were about 100 red wolves
in zoos involved in the program, currently there
are about 300
• slowly being reintroduced into wild
• One of the key questions about the red wolf is whether it is
even a distinct subspecies of wolf. There was divided
opinion, ranging from some who believed it is really a
separate and distinct species, to others who believe its gene
pool has been so diluted by hybridization with coyotes that it
does not deserve any protection or preservation.
• Multivariate morphological genetic analysis doesn't help
much in separating out the red wolf. Wayne (1992) used 15
morphometric characters which aligned on two principal
components.
The Algonquin Park Eastern Wolf (Canis lyacon)
• Wolves of Algonquin Park are smaller (60-68cm at shoulder)
than gray wolves and more uniform in colour.
• preys on deer, moose and beaver
• hunting ban in place since 2001 in and around the park
• Recent molecular genetic data suggests they are closely
related and possibly the same species as the red wolf
• Microsatellite DNA and MtDNA analysis suggest that these
wolves are not the result of hybridization between gray
wolves and coyotes.
• The MtDNA did include coyote-related DNA, but rapid
divergence by mutation indicates that both originated from a
line that diverged 150,000-300,000 years ago.
• Neither American red wolves nor Algonquin
wolves incorporated gray wolf sequences.
• popular wolf calling events on summer
evenings by park personnel
• province compensates farmers for lost livestock
The Florida Panther
The Florida panther, Felis concolor coryi, has some
genetic parallels to red wolf. Some of the remaining
natural population of panthers carries genes introduced
from a (non-sanctioned) released South American
puma. The total population is 80 - 100 cats (as of
2006). The Florida panther was distributed from Texas,
through the SE USA, though now it is found only in
Florida. Males range 400 square miles, females 50.
Genetic analysis indicates that they fall into two distinct
stocks. A map indicates the places where panthers
have been observed and, based on radio collar
locations, the principle areas utilized by the two groups.
One uses the Everglades. This group was genetically
corrupted by either South American pumas or their
captive offspring. Distinct South American genes now
persist in the Everglades group.
The second group, living around Lake Okeechobee, is
not corrupted, and carries none of the South American
genes. Given the scattered observations of individual
panthers well outside their principal use areas, that is
remarkable. You can see that there is a small presence
of mtDNA B in the Big Cypress swamp population.
The red outline indicates Florida panther habitat. Each
black dot within indicates a radiocollar localization. The
figure comes from Cox et al. 2006. Note the very small
number of observations of panthers between the two
main population areas.
The remnant panther populations carry a number of
signs of what may be inbreeding depression. They
almost uniformly have a right angle kink in their tails
near the tip and a cowlick in the fur along their backs,
almost all males are cryptorchid (only 1 testicle
descends), sperm collected from males shows a very
high percentage of defective cells (~90%), and heart
murmurs are were observed in every kitten born in
1990, as well as 30% of adults examined.
However, even with these problems, births have been
more numerous than deaths since 1987. Even that is
surprising, since measures of hormonal condition of
males and females suggest extensive male feminization
due to exposure to xenobiotic chemicals, particularly
(likely) PCBs and other estrogenic compounds.
All panthers
Everglades panthers
Is there demographic evidence of inbreeding?
A comparison of litter size at birth from 1985 to 1993 to
numbers of juveniles of 4-12 months age showed only
very low juvenile death rates. At birth, litter size
averaged 1.92 kittens (n=25); at 4-12 months an
average of 1.89 kittens remained. Depending on which
data points you put into a calculation of lx, you can get
from .84-.87 as one year survivorship. Considering
animals of all ages, annual survivorship was 0.82. All
these are high values, not indicative of a survivorship
cost to inbreeding.
Is there other evidence that inbreeding is occurring?
There is evidence to suggest inbreeding may be or
become important. It’s evidence that females don’t
disperse far enough from their natal territories to avoid
inbreeding (Maehr, et al. 2002). Females move, on
average, only 20.3 km, and this is less than the width of
one home range. Males go further (68.4 km).
Nevertheless, there is no evidence of successful
immigration or emigration from or into existing
populations from any others. Both distances are far
smaller than those for cougars from further west.
So, what was done to develop an SSP?
As part of the species survival program, eight adult
female Texas cougars were recently released in
southern Florida to increase the influx of outbred genes
into the population. The introduction was suggested by
the results of a modeling study using a PVA model called
VORTEX, which indicated an 85% probability of species
extinction within the next 25 years based on known
demographics.
The introduction seems to have been successful. The
introduced Texas cougars have died, but 5 successfully
reproduced with Florida panthers, producing at least 20
kittens as of 2004.
There was an opposite concern. Some researchers
worried over the potential for outbreeding depression.
We will find out over the next few years if this happens
since outbreeding depression is usually evident in F1 or
F2 generations. There is no current evidence from the
F1 generation of that depression.
A predictive study by Hedrick (1995) suggested that
genetic variability would be markedly increased and
inbreeding decreased without loss of adapted Florida
panther alleles.
The goal for the introduction of other pumas and
captive breeding program was to establish a population
of 130 panthers by 2000 in a combination of captive
breeding and wild groups, and 500 by 2010.
That is a minimum viable population approach,
predicting 95% probability of survival in the wild for 100
years. The wild population continues to remain below
100 animals in 2005-6 (based on the most recent report
I could find).
The Florida panther ‘supplementation’ by Texas pumas
is a chance to consider how demography and genetics
can be used together to assess the likely success of
conservation practices. Alexandre et al. (2007) present
theory and practice.
In theory, how does inbreeding affect population growth?
The replacement rate, R, is reduced (B is lethal
equivalents, f is the inbreeding)
Rt  R0 e
 Bf t
The amount of inbreeding is determined by effective
population size:
f t 1  1 / 2 N e   1  1 / 2 N e  f t
The reduced R affects population growth rate:
N et 1  Rt N et
Here’s what the result looks like – growth with and
without inbreeding depression…
Solid lines: R0 = 2.25, B = 1,
N0 = 2
Dashed lines: R0 = 1.25, B = 1
N0 = 10
The idea: ???
With small effective population size and slow growth
(typical of large carnivores), mildly deleterious mutations
are likely to become fixed and accumulate, increasing
genetic load (e.g. the various anomalies in Florida
panthers). The gradual decrease in fitness leads to what
has been termed “mutational meltdown”.
In a species like Florida panther, how many should be
released to markedly enhance probability of
persistence? The quoted number in Alexandre et al.
(2007) is at least 1 – 6 individuals per year, and to avoid
loss of local adaptation <10. Note the number of Texas
panthers actually released! The individuals released
came from a large, but distant population, and were
‘chosen’ from different areas to maximize their genetic
diversity.
Genetic and demographic models conditions
determined the details of the release.
1. Genetic drift had fixed mildly deleterious alleles in the
remaining natural population, resulting in low
fecundity.
2. Demographic evaluation led to the release of young
adult females.
3. Total release size was 8 individuals. The rate of
introduction was 20% ‘injected’ gene flow from outside
in the first generation, and 2.5% thereafter.
4. The data you’ve already seen points to success
numerically (population increase), in expanded range
for the supplemented population, and in genetic
‘health’.
However, there was another problem beyond genetics
and demography. The food of Florida panthers
apparently includes raccoons. It was discovered that
Florida panthers tended to have high levels of Hg in
their bodies, as well as other contaminants.
The mercury contamination (probably from its food
(raccoons and other mammals, themselves
contaminated by agricultural chemicals), affects kidney
physiology and brain development.
Panther tissues have also been shown to contain
moderate to high levels of p,p'-DDE, methoxychlor, and
other organochlorine chemicals. The listed compounds
and others are known to act as endocrine disrupters. In
other species they can cause feminization of males and
impair female reproductive endocrinology and cycles.
So, some of the observed low fecundity may have been
due to factors unrelated to the genetics and
demography characteristic of small populations.
Interestingly, there was no significant difference in
estradiol concentrations among groups comprised of
normal males (both testicles descended), cryptorchid
males, and females. What this means is not clear.
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