Download Case Studies I: ferrets, cheetahs, spotted owl

Case Study I
Conservation Biology 55-437
Lecture 18
April 1, 2010
Black-footed ferret (Mustela nigripes)
• member of the weasel family
• listed as threatened in the US in 1967 and endangered in 1973.
• An initial recovery plan was devised by the US Fish and Wildlife
Service in 1978.
• Decline of the species coincided with, and may have been caused by,
the tremendous decline (90-95%) in prairie dog abundance earlier this
century.
Prairie Dogs are Considered Keystone Species
• are the primary (90%) food of black footed ferrets, swift fox, the
golden eagle, the badger, and the ferruginous hawk.
• species, such as the mountain plover and the burrowing owl rely on
prairie dog burrows for nesting areas.
• grazing species such as bison, pronghorn and mule deer may prefer
the vegetative conditions after prairie dogs have foraged through the
area.
• Prairie dogs were targeted as pests because their
burrows damaged farm implements and tractors.
Historically, has been thought that burrows could
harm livestock.
• Encroachment of development on habitat.
• Prairie dogs also appear to have suffered from
introduction of diseases.
• In 1964, small population discovered in S. Dakota
• Studied and in 1971 brought into captivity for
captive rearing attempts.
• 1978 end of known ferret existence in wild.
• re-discovered at a single site in Wyoming in 1981.
• A Species Survival Plan (SSP) was developed based
on captive propagation to eventually re-release
ferrets into the wild.
• By 1985, black footed ferrets were limited to ~130 individuals in one
population at Meteetsie, Wyoming.
• The other population (from South Dakota) had been placed in a
captive breeding program without success. ( went extinct; good
conservation biology?)
• The Wyoming population was surveyed but not captured. This
population suffered after plague was discovered among its prairie dog
prey. Six ferrets were captured for a captive breeding program; all died
of canine distemper.
•1985: Six additional ferrets captured from wild. Population low
reached with N = 4 known wild survivors and 6 in captivity.
• During 1985-1986: No reproduction in captivity but 2 litters at
Meeteetse. Decision made to capture all wild individuals bring them
into captivity.
• Goals were quickly set to maintain as much (90%) genetic diversity
as possible for a minimum of 50 years. Two litters of kits were born
in 1987. Since then 4800 kits have been born in captivity (Grenier
2007).
• In 1988 the captive population was subdivided into two isolated
groups (to minimize chances of catastrophic extinction of the
species).
• By the early 1990s the captive breeding program was producing
>100 kits annually at 6 captive breeding sites (including the
Toronto zoo).
• Ferrets were reintroduced to southern Wyoming in 1991 (228
ferrets over the period 1991-4).
• By 1992 some individuals (12%) survived the winter and
reproduced successfully in the wild.
• Coyotes appeared to be the primary predator and source of
mortality, and survival was only moderate (20-25% for 30 days).
• The population is growing and introductions of ferrets to sites in
Wyoming (Shirley Basin – 228 ferrets over 1991-4), in South Dakota
(90 ferrets) and one in southern Montana (78 ferrets) in 1994-5.
• In the Shirley Basin the release was thought to be failing. By 1996
there were <25 ferrets remaining from the release, and monitoring
became sporadic. But then in 2003 there were 52, and continued
increase found an estimated 223 in 2007.
• In 2005 the estimated ferret population in South Dakota was 400.
Verification of this estimate has not proved easy.
• Since reintroductions in Wyoming and South Dakota, a number of
additional successful reintroductions have occurred:
• 186 released beginning in 2001 in northwest
Colorado; in January 2006 wild reproduction found
• Continuing releases in Aubrey Valley, Arizona must have been
successful. In 2005 14 ferrets were counted that must have been born in
the wild (no microchip marker).
• There are four other active re-release sites (8, aiming for 10 in all)
being monitored for success in the U.S. and Mexico. The SSP calls for
10 populations with 30 breeding adults in each. The species will then be
downgraded to threatened.
Location / Year introduced and
population as of 2010
1. Shirley Basin (1991; > 30)
2. Conata Basin/Badlands (1994; > 30)
3. UL Bend Refuge (1996; < 30)
4. Aubrey Valley (1996; < 30)
6. Coyote Basin (2000; < 30)
7. Cheyenne River Reservation (2000; > 30)
8. Wolf Creek (2000; < 30)
9. 40-Complex (2000; < 30)
10. Janos, Chihuahua (2000; < 30)
11. Rosebud Sioux Reservation (2000; < 30)
12. Lower Brule Reservation (2006; < 30)
13. Wind Cave National Park (2007; < 30)
14. Logan County (2007; < 30)
15. Northern Cheyenne Reservation (2008; < 30)
16. Espee Ranch (2008; < 30)
• No ferrets have been observed in Canada since
1937.
• The reintroduced ferrets are (in the language of the
U.S. Endangered Species legislation) a nonessential,
experimental population. Under this designation, the
animals are protected at the reintroduction site, but
are left unprotected should they move off site.
Dynamics of the Shirley
Basin reintroduction:
In 2007, Grenier et al. used demographic modeling to
determine the keys to population persistence. They expected
adult survivorship and long-term fertility were important.
• first year survival and early fertility were the keys.
For conservation, that means long-term monitoring may not
be necessary but need to maintain early survival and fertility.
African cheetah (Acinonyx jubatus):
The cheetah was once found on 5 continents. At the
turn of the 20th century it occurred in both Africa and
Asia). Today it is limited to Africa and a small
population in Iran.
The historical distribution:
The current distribution:
The cheetah population is estimated to have declined by 50%
in abundance (to ~10,000 - 20,000) by the mid-1970s from
the previous decade, largely as a result of habitat destruction
and hunting by humans. Current population may now be
between 1,500 and 25,000 individuals.
There may be another contributing factor. In 1983, O‘Brien
and colleagues reported that cheetahs had remarkably little
genetic variation. 55 captive and wild-caught cheetahs
derived from two separate populations were monomorphic at
all 47 allozymes surveyed.
The cheetah had the lowest frequency of polymorphic loci
(0.0) and lowest average heterozygosity (0.0). Overall, the
cheetah had between 10 and 100 times less genetic
variability than other mammals.
• Patterns of low genetic diversity in cheetah are
attributed to a severe population bottleneck (O’Brien
1983). This bottleneck may have followed decimation
of the population by legal and illegal hunting by African
cattle farmers about 100 cheetah generations ago.
Merola (1994) compared the
cheetah's genetic variability with
that of other carnivores
vertebrates. Of 24 terrestrial
carnivores surveyed, 8 had no
heterozygosity (H = 0), while
the remaining ones averaged
H = 0.042 (vs. H = 0.014 for
the cheetah).
Could this low genetic diversity be affecting the
population?
• Genetic theory predicts that inbreeding among members
of small populations will reveal deleterious recessive
alleles.
• Deleterious recessive alleles can manifest in:
1. High infant mortality
2. Lowered fecundity
3. Higher susceptibility to disease
Are these effects witnessed in cheetahs?
High infant mortality
• Cheetah also experienced high infant mortality rates.
O’Brien (1983) cited high infant mortality among
captive individuals and noted that such mortality was
consistent with effects of low genetic diversity. So,
could this explain what is happening in the wild?
High infant mortality
• O’Brien et al. (1985) noted that infant mortality rates for
inbred and non-inbred cheetah mating (in captivity) did not
differ significantly, suggesting that
inbreeding has no
pronounced effect
today (largely
because strong effects
were evident earlier) –
i.e. genetic diversity
was already low.
High infant mortality
• Kelley et al. (1998) radio-collared female cheetahs in
the Serengeti and followed them as they traveled
throughout their 800-km2 home ranges. Identified
birthing sites (lairs).
• Entered lairs when adults were away and counted
young. Regular monitoring showed that young suffered
from high mortality rates (80 %).
• Most mortality was predation related – not genetic
defects.
Kelley et al. 1998. Journal of Zoology 244:473-488
Lowered fecundity
• Reproduction in captivity is low – as of 1986, only 17
of 108 females and 12 of 85 males had bred in zoos
(~ 84 % of captive cheetah do not breed)
Does this mirror natural conditions?
Lowered fecundity
• Wild cheetahs are polyestrus,
cycling ~ every 12 days with a
gestation period of ~ 93 days.
• For wild cheetahs, high
numbers of females breeding
and rapid rates of litter
production suggest that the
reproductive physiology of
either sex is compromised.
Susceptibility to Disease
• O’Brien et al. (1985) cited a field study of disease
sweeping through a successful felid breeding colony in
Oregon.
•Within this colony, 60% of the captive cheetahs died
from corona virus associated diseases.
• noted that this mortality rate was consistent with, but
not proof positively a consequence of genetic uniformity.
Susceptibility to Disease
• Heeney et al. (1990) sampled captive and wild cheetah
and found ~20 to 60% tested seropositive for a number
of infectious agents.
• Shows variability in cheetah response to disease –
some individuals can mount a response to exposure.
• Merola (1994) concluded that the lack of breeding
success and high infant mortality rates were due to poor
captive breeding program procedures but may still be
linked to homozygosity (maternal neglect, cannabalism:
Simberloff 1988).
• She argued that as long as recessive alleles (deleterious)
were slowly purged from the population, the resulting
population could be relatively homozygous but without
inbreeding effects.
So, is low genetic diversity not a problem ?
More recent molecular genetics (Marker et al. 2008) indicate
that there is limited genetic variability and differentiation
among cheetah populations from Namibia, but that there is
panmixis across large areas. The distance between captures of
close relatives indicates how far cheetahs may move:
Relationship Mean Distance between captures (km)
Dam & daughter
13
Dam & son
116.38
Sire & daughter
93.50
Sire & son
99.06
Sibs
121.00
Overall
90.66
May be a problem for some populations but are trumped
by environmental and demographic problems.
Genetic considerations typically impact on a slower time scale.
•For Namibian cheetahs, habitat conservation and
promotion of natural dispersal and gene flow is critical
to species conservation.
• habitat destruction has resulted in population densities
of one cheetah per 6 km2 rather than the old rate of 1 per
100 km2
• High densities facilitate transmission and spread of
disease and 'focusing' of cheetah predators in the small
reserves.
Northern Spotted Owl (S. occidentalis caurina):
The owl is rare (low abundance) even
in the best of habitats. In southwestern
B.C., the owl was found at 14 sites, with
a total population of as few as 100
individuals (Dunbar et al. 1991). They
attributed its rarity to habitat
destruction (logging, fires, development) and
to Barred Owls which live in the same old-growth habitat and
which respond aggressively to spotted owl calls (thus
potentially limiting its habitat availability).
“If we have learned one thing about the influence of
the Spotted Owl on wildlife conservation, it is that the
solution to conserving a threatened species that is still
relatively widespread is exceedingly complex.”
--- Gutiérrez et al. 1995 ---
Gutiérrez, R. J., A. B. Franklin and W. S. Lahaye. 1995. Spotted
Owl (Strix occidentalis), The Birds of North America.
In the USA, the northern spotted owl has pitted
environmentalists against loggers. The case was
resolved during summer 1995 by the conservativeleaning Supreme Court in favour of preservation of
essential lands for owl habitat. Habitat loss in the U.S.
has been extensive:
The result of the conflict was the development of the
Northwest Forest Plan to conserve diversity in northwest
forests in general, as well as to protect the spotted owl.
Origins of Conflict
• Historical practice of clearcut logging in Pacific
Northwest.
• U.S.F.W.S. reviewed the status of the Northern
Spotted Owl in 1982 and 1987 - concluded it did not
warrant listing as threatened or endangered.
• Reviews in 1989 and 1990 proposed listing as a
threatened species under the ESA. Loss of old-growth
habitat was cited as the primary threat.
• Listing was implemented on June 23, 1990.
• Logging in national forests was stopped by court
order in 1991.
Origins of Conflict
• Logging industry estimated that ~ 150,000 jobs would
be lost because of logging reductions.
• In fact, the logging industry had been dwindling
significantly due to loss of old-growth forest and
protective legislation.
• Listing was implemented on June 23, 1990.
• Logging in national forests was stopped by court
order in 1991.
Bart and Forsman (1992) and Bart (1995) looked at
spotted owl density and breeding success in habitats
of differing quality in Washington and Oregon. In
sum, the higher the percentage of old growth forest
(good habitat), the higher the owls/km2, breeding
pairs/km2, young fledged/km2, young fledged/km2,
and adult survival.
To provide clear answers to key questions about the
spotted owl populations, Murphy and Noon (1992)
formulated a number of important, testable
hypotheses regarding the owl:
1.Is the owl population growing (is lambda [finite
rate of growth] >1? Answer: No
2.Do owls differentiate among forests of different
ages or structures. Answer: Yes The owls prefer
habitats based with old-growth forest disproportionate to the abundance of this habitat type.
3.Habitat type selected by the owls has not changed
in abundance. Answer: No, it has decreased.
4. The probability of persistence is not related to the
extent of its geographic distribution. Answer: It is.
5. There is a relationship between HCA (habitat
conservation area) size and its owl carrying capacity.
Answer: Yes.
6. A relationship exists between habitat fragmentation
and persistence likelihood of species using that
habitat landscape. Answer: Yes
7. Distance between habitat patches has a bearing on
dispersal success of juvenile owls. Answer: Yes,
there is a very strong relationship.
Probability of successful owl dispersal
versus distance between suitable
habitat patches
Based on these answers, a map of
suitable habitat patches for spotted
owl conservation was constructed
for Oregon and Washington:
More Recent
• A specific Northern Spotted Owl Recovery Plan was
developed in 1992 by team of nonscientists.
• Plan specified de-listing criteria and formalized
recovery strategies.
• The U.S. Federal Government took no action.
• Followed by series of alternative plans.
- 1994 Clinton’s Northwest Forest Plan
• Presently, ecosystem plan on federal lands being
implemented.
What additional problems remain?
• 2007 USFWS considered owl still threatened but suggested
that the cause had changed – invasion of habitat by barred
owls.
• Habitat destruction is clearly key – not just logging, but
forest fires. The late successional forest areas most important
to spotted owls also have fuel conditions that make fires
likely. Ager et al. (2007) showed via modeling that treatment
of fuel conditions on relatively small proportions (20%) of old
growth forest areas resulted in a 44% reduction in the
probability of spotted owl habitat loss .
• Owl populations continue to decline at ~ 4% / year.
What have we learned?
Despite continued losses (~ 4% decline/year) Spotted
Owl issue has been instrumental in facilitating
additional learning in fields of:
•
•
•
•
•
population genetics
population dynamics
metapopulation dynamics
reserve design
extinction and viability analyses
References
Ager, A.A. et al. (2007) Modeling wildfire risk to northern spotted owl
(Strix occidentalis caurina) habitat in Central Oregon, U.S.A. Forest
Ecol. Manag. 246:45-56.
Bart, J. 1995. Amount of suitable habitat and viability of northern spotted
owls. Conservation Biology 9:943-946.
Bart, J. and E.D. Forsman. 1992. Dependence of northern spotted owls
(Strix occidentalis caurina), on old-growth forests in the western USA.
Biological Conservation 62:95-100.
Crooks, K.R., M.A. Sanjayan, D.F. Doaks. 1998. New insights on
cheetah conservation through demographic modeling. Conservation
Biology 12: 889-895.
Dunbar, D.L. et al. 1991. Status of Spotted Owl, Strix occidentalis, and
Barred Owl, Strix varia, in southwestern British Columbia. Canadian
Field Naturalist 105:464-468.
Durant, S.M. et al. 2007. Relating long-term studies to conservation
practice: the case of the Serengeti Cheetah project. Conservation
Biology 21:602-611.
Grenier, M.B. et al. Rapid population growth of a critically endangered
carnivore. Science 317:779.
Heeney, J.L. et al. 1990. Prevalence and implications of Feline
Coronavirus infections of captive and free-ranging Cheetahs. Journal of
Virology 64:1964-1972.
Laurenson, M.K. et al. 1995. Extrinsic factors and juvenile mortality in
cheetahs. Conservation Biology 9:1329-1331.
Lubben, J. et al. 2008. Management recommendations based on matrix
projection models: The importance of considering biological limits.
Biological Conservation 141:517-523.
Marker, L.L. et al. 2008. Molecular genetic insights on Cheetah
(Acinonyx jubatus) ecology and conservation in Namibia. J. Heredity
99:2-13.
May, R.M. 1995. The cheetah controversy. Nature 374:309-310.
Menotti-Raymond, M. and S.J. O'Brien. 1993. Dating of the genetic
bottleneck of the African cheetah. Proceedings of the National
Academy of Science 90:3172-3176.
Merola, M. 1994. A reassessment of homozygosity and the case for
inbreeding depression in the cheetah, Acinonyx jubatus: implications for
conservation. Conservation Biology 8:961-971.
Murphy, D.D. and B.R. Noon. 1992. Integrating scientific methods with
habitat conservation planning: reserve design for northern spotted owls.
Ecological Applications 2:3-17.
O'Brien, S.J. et al. 1983. The cheetah is depauperate in genetic
variation. Science 221:469-462.
O'Brien, S.J. et al. 1985. Genetic basis for species vulnerability in the
cheetah. Science 227:1428-1434.
O'Brien, S.J. et al. 1987. East African cheetahs: evidence for two
population bottlenecks? Proceedings of the National Academy of
Science 84:508-511.
O'Brien, S.J. 1994. The cheetah's conservation controversy.
Conservation Biology 8:1153-1155.