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I. Overview
II. Introduction
III. Purpose of and Need for Action IV. Existing Conditions
- A. Population Size
B. Location
C. Habitat
D. Population Health
- 1. Lost Gene Flow
2. Genetic Reduction
3. Genetic Health
4. Spermatozoal Traits
5. Cryptorchidism
6. Congenital Heart Defects
7. Immune Deficiencies
8. Conclusions
9. Concerns over Genetic Health
F. Recovery Thrusts
G. Genetic Restoration
H. Intercrossing For Genetic Restoration
I. Recovery Plan Revision
J. Genetic Management Plan
K. Environmental Contaminant Concerns
L. Scoping
I. OVERVIEW
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The Florida panther, Felis concolor coryi, is one of the most
endangered large mammals in the world. A small population in southwest
Florida estimated to number 30-50 adults represents the only known
remaining wild population of an animal that historically ranged throughout
most of the southeastern United States - from Arkansas and Louisiana
eastward across Mississippi, Alabama, Georgia, Florida and parts of South
Carolina and Tennessee.
Geographic isolation of the taxon, habitat loss, population decline and associated inbreeding have resulted in significant loss of genetic variability and health of the population. Natural gene exchange which historically occurred between the Florida panther and other contiguous subspecies of Felis concolor ceased to occur when the panther became geographically fragmented from other population of its species.
Gene flow occurs as individuals disperse among populations and breed. As dispersal is the natural mechanism for gene exchange and maintenance of genetic health within populations, those same dispersing breeders minimize the occurrence of inbreeding within populations. Inbreeding accelerates when dispersing breeders can no longer emigrate into small, isolated populations, resulting in genetic depression, declining health, reduced survivability, low numbers, and eventual extinction.
The above scenario is recognized as part of the extinction process. It is this biological circumstance that perhaps most affects the health and survivability of the Florida panther as a population.
While other human related factors affect the health of the panther's environment, it is now clear that genetic variability and health of the Florida panther must be restored for the taxon to survive even with adequate habitat preservation and other enhancement measures. Genetic restoration of the Florida panther is possible and feasible, because its historic source of genetic variability, from which it is now isolated, still exists abundantly throughout much of western North America.
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The Florida panther's existence is severely threatened by both rapid and
gradual extinction processes. Factors of concern include habitat loss and
fragmentation, environmental contaminants, prey availability, human
related disturbance and mortality, disease, and genetic erosion.
Population viability analysis projections indicated that under existing demographic and genetic conditions the Florida panther will likely be extinct in only a few decades (24-63 years, Seal et al. 1992). Actual time to extinction could be accelerated significantly by the occurrence of a catastrophic population reducing event.
Extinction of the Florida panther can be avoided only if actions to enhance existing genetic conditions, along with programs to expand the sold remaining wild population (numbers and distribution), are implemented and are successful.
Programs to expand the population must included actions to preserve remaining habitats considered essential to meeting the needs of a self-sustaining population in south Florida and actions to reestablish populations and preserve habitats elsewhere within the panther's historic range. Measures to enhance genetic conditions must include actions to preserve existing genetic resources, restore diversity and viability, and manage for inbreeding problems. Consideration must be given to strategies designed to restore historic gene flow.
- A. Purpose - The
purpose of the
proposed action is to implement a genetic restoration and management
program that is designed to improve the genetic health, survivability and
recovery potential of the endangered Florida panther (Felis concolor
coryi). The proposed program involves a strategy designed to restore
lost historic gene flow into the panther from another F.c.
subspecies. Under the proposed action, genetic restoration would be
carried out directly in the sole remaining wild population, which is
located in southern Florida.
It should be clearly understood that the intent of the proposed action (translocated a limited number of non-Florida individuals into the population) is to improve genetic conditions and population health of the Florida panther. It is not an action to merely "add numbers" to the population. The intent is that future offspring will be healthier and thus provide security against extinction initially, and ultimately provide enhanced opportunities to achieve other key recovery tasks, such as population reestablishments. Though population reestablishments are critical to recovery of the panther, they are not a part of the proposed action.
B. Need - Extinction of the Florida panther can be avoided only if programs to enhance existing genetic conditions and expand the sole remaining wild population (expand numbers and distribution), are implemented and are successful.
A lack of suitable, unoccupied habitat (for subadult dispersal) (Maehr 1990a) within the range of the present radio-instrumented segment of the wild population would be expected to prevent significant population growth in southwest Florida (area south of the Caloosahatchee River). However, landscapes deemed capable of supporting panther remain within other areas formerly occupied by the Florida panther, and programs are presently underway to identify and evaluate potential population reestablishment sites range-wide and to develop technologies needed to successfully expand the existing wild population (reintroduction experiments).
The program proposed herein is designed specifically to address the need to enhance existing genetic conditions in the Florida panther. Enhanced genetic conditions would be expected to not only improve the overall health and fitness of the Florida panther, but would be expected to result in improvements in the high incidence of maladaptive traits which include reproductive and medical abnormalities. These conditions include high levels of sperm abnormality, high incidence of cryptorchidism, and congenital heart defects. Details on these conditions are provided below.
- A. Population
Size - The sole
known remaining extanct population, which is located in southern Florida,
is estimated to number 30 to 50 adult panthers. Because suitable habitat
in south Florida is limited, this population can not be expected to
achieve significant population growth via natural dispersal processes.
The radio-instrumented segment of this population (n=16) is presently
comprised of 9 females and 7 males (November 1, 1994). The captive
population is presently comprised of 5 males and 4 females.
B. Location - The present radio-instrumented segment of the wild population is centered around Collier and Hendry Counties in southwest Florida. Radio-instrumented panthers have also utilized habitats in Broward, Dade, Glades, Highlands, Lee, Monroe, and Palm Beach Counties (Figure 1). A total of 56 panthers have been radio-instrumented since 1982. All but one of these individuals occupied landscapes south of the Caloosahatchee River.
C. Habitat - Panthers utilize large forested tracts comprised of mixed swamp forest, cypress swamp, sawgrass marshes, mesic hammocks, sand pine scrub, and pine flatwoods (Maehr 1990b). Panthers prefer uplands, especially hardwood hammocks and pine flatwoods, over wetland forest cover (Maehr 1990a). Maehr (1990b) reports that there are approximately 2.2 million acres of occupied panther range in south Florida and that approximately half of the known breeding distribution was comprised of landscapes under private ownership. Maehr (1990a) also reports that, based on telemetry data, there is a lack of unoccupied, suitable habitat for subadult dispersal. This suggests that available landscapes south of the Caloosahatchee River are at or near carrying capacity under existing habitat conditions.
D. Population Health (as may be related to genetic conditions) - The Florida panther population exhibits multiple physiological abnormalities that are likely a consequence of recent close inbreeding. This inbreeding has resulted in a high incidence of maladaptive traits which include reproductive and medical abnormalities. Furthermore, the Florida panther has suffered from numerous health problems and infectious diseases that may be a consequence of a defective immune system. Population viability analysis projections indicate that under existing demographic and genetic conditions the Florida panther will likely be extinct in only a few decades (24-63 years, Seal et. al. 1992). Actual time to extinction could be accelerated significantly by the occurrence of a catastrophic population reducing event.
Lost Gene Flow - Natural gene exchange which occurred historically between F.c. coryi and other contiguous populations of Felis concolor ceased to occur when the panther became geographically isolated from other populations of the species. Gene flow occurs as individuals disperse among populations and breed. Just as dispersal is the natural mechanism for gene exchange and maintenance of genetic health within populations, those same dispersing breeders minimize the occurrence of inbreeding within populations. Inbreeding accelerates when dispersing breeders can no longer emigrate into the fragmented population, resulting in inbreeding depression, loss of genetic variation, declining health, reduced survivability, lower numbers and eventual extinction. It is this biological circumstance that most seriously affects the health and survivability of the Florida population.
Literature indicates that gene exchange between the Florida panther (Felis concolor coryi) and other F. concolor subspecies occurred from the north through F. c. cougar, and from the west and northwest through F. c. stanleyana and F. c. hippolestes (Young and Goldman 1946).
The natural gene flow ceased at the time the Florida panther became geographically isolated, likely a century or longer ago. Isolation and accompanying population declines and inbreeding have resulted in the loss of genetic diversity and health. Recent population viability analyses project that genetic heterozygosity is being lost at a rate of approximately 6% per generation (Seal et al. 1992). Low heterozygosity levels (0.019) indicate that the Florida panther is inbred and has lost approximately half of its genetic diversity (Roelke 1990).
Genetic Reduction - Based on results of genetic testing, as summarized below from Roelke et al. (1993), surviving Florida panthers have experienced substantial inbreeding and concomitant loss of genetic diversity in their recent history. The level of mtDNA variation in the Florida panther is the lowest reported in any similarly studied feline population, including leopards, cheetahs, and other pumas subspecies. Electrophoretic results indicated that the Florida panther had less variation than any other puma subspecies and is nearly as low as the level of allozyme variation reported in the two cheetah subspecies. DNA fingerprint variation seen in the Florida panther is nearly as low as the extremely compromised genetic variation in Asiatic lions from the Gir Forest Sanctuary in India.
Genetic Health - The U.S. Fish and Wildlife Service is concerned that the overall genetic health of the Florida panther may now be at a point where the panther's continued existence is doubtful without a proactive genetic restoration program. This concern is supported by several physiological impairments displayed by the population as summarized below.
Spermatozoal
Traits: Semen
quality and endocrine and reproductive functions have been shown to be
adversely affected in some inbred lines of several species, including
mice, cats, 2 lion subspecies and cheetahs (Wildt 1994). Comparative
reproductive analyses of seminal traits in five feline species, revealed
that Florida panther males display some of the poorest seminal quality
traits ever recorded for any felid species or subspecies (Barone et al.,
1994). Total motile sperm per ejaculate in the Florida panther is 18-38
times lower than in other puma subspecies, 30-270 times lower than in
other felids and 30 times lower than in the cheetah. Although cougars and
other large felids tend to produce high proportions of morphologically
abnormal sperm, the Florida panther has a significantly greater frequency
of malformed spermatozoa (average 93.5% per ejaculate) than any other
subspecies; particularly noteworthy was a 42% incidence of acrosomal
defects, a trait that renders sperm deficient in fertilization potential
(Barone et al., 1994). Seventy-five percent of the sperm exhibit
severe deformity and are classified as having primary
abnormalities (Roelke 1990). Compared to Felis concolor from
Texas, Colorado, Latin America, and North American zoos, the Florida
panther has lower testicular and semen volumes, poorer sperm progressive
motility, and more morphologically abnormal sperm, including a higher
incidence of acrosomal defects and abnormal mitochondrial sheaths (Barone,
et al. 1994).
Cryptorchidism: Cryptorchidism
is heritable and is suspected to result from a sex-limited recessive (or
possible dominant) autosomal gene in several domestic species: dog,
sheep, swine, and cat (Romagnoli, 1991; Burns & Fraser, 1964; Claxton &
Yeates, 1972; McPhee & Buckley, 1934). Sixty-five percent of free-ranging
Florida panthers of Big Cypress genetic lineage are cryptorchid (as of
6/30/94), while there has been only 1 cryptorchid male of 7 males of
Everglades lineage (Dunbar, 1994). Cryptorchidism has not been observed
in only two of more than 50 captive males, one in Chile and one in a US
zoo (Roelke et al., 1993). Circulating testosterone concentrations were
lower in male Florida panthers with only one descended testicle than in
those with two, whereas testosterone levels in Florida panther with two
normally descended testicles were no different from males in other cougar
populations (Barone et al., 1994). In addition, cryptorchid male Florida
panthers tend to produce fewer motile sperm per ejaculate than normal
males: 0.54 x 10^6 compared with 2.19 x 10^6 (Barone et al., 1994). A
high incidence of cryptorchidism in the population has been observed in
the last two decades, a period in which there have been a number of
documented mating between close relatives (Roelke et al., 1993). These
observations document the rapid rise toward genetic fixation of a
maladaptive genetic trait in a small population that continues to inbreed.
Cryptorchidism has not been reported previously in non-domestic cats of
any species (Roelke et al. 1993). Cryptorchidism is believed to be a
manifestation of inbreeding. In miniature Schnauzer dogs, for example,
intentional inbreeding resulted in an incidence of 67% cryptorchidism (Cox
et al. 1978). Until 1992, all panther males known to possess this
abnormality were unilaterally cryptorchid, meaning only one testicle had
not descended properly into the scrotum. This condition does not normally
render the individual incapable of reproducing. However, from an overall
population health and genetic standpoint it is of significant concern.
This concern is magnified in the Florida panther because of the many other
factors threatening panther survival. In 1992, concern over
cryptorchidism heightened considerable when one of four newly captured
males was determined to be bilaterally cryptorchid (neither testicle
descended properly) and a second had a single, significantly smaller,
partially descended testicle (Roelke and Glass 1992). Bilateral
cryptorchid individuals are functionally sterile.
Congenital Heart
Defects: Life
threatening congenital heart defects have been observed in the population
(Roelke and Glass 1992). Atrial septal defects (ASD), termed patent
foramen ovale, were found in 5 out of 55 documented Florida panther
mortalities from 1972 through July 1994 (Roelke et al. 1993; Dunbar,
personal communication, 1994). This defect may have contributed to death
in 4 out of 5 of these cases. ASD has been observed in several species
including human (ASD is the most common congenital heart defect in human
adults) (Braunwald 1992), but had not previously been observed in cougars
and only rarely in domestic cats (Bolton & Lui 1977). The etiology of ASD
is not well understood, but certain cases in humans suggest an autosomal
dominant mode of inheritance (Lynch et al. 1978; Mascia and Moller 1987).
Heart murmurs occur in Florida panthers, sometimes at high frequencies
(80%, compared with a frequency of occurrence of only approximately 4%
with other cougar subspecies [Roelke et al. 1993]); however, the
relationship between ASD and heart murmurs is not clear. Recently, hypo-
and hyper-vitaminosis A have been ruled out as potential causes of cardiac
abnormalities in Florida panthers (Dunbar 1994). The etiology of the
cardiac defects is unknown, however; there may be a genetic explanation.
Immune
Deficiencies:
Additionally, some scientists now have concerns over what appears to be an
inability of some, apparently "healthy" individuals to overcome exposure
to infectious agents that would normally not be expected to result in life
threatening/terminal conditions; raising questions of possible immune
deficiencies (Seal et al. 1992). The importance of population genetic
diversity for loci involved in immune responses has been empirically
demonstrated in several species (Roelke, et al. 1993). Through 1992, at
least eight panther mortalities were attributed to infectious pathogens,
although no single agent had caused widespread mortality during the study
period (Roelke et al. 1993).
Conclusions - Based
on available date,
the overall genetic diversity of the panther is markedly reduced relative
to other puma subspecies. In concert with these genetic measures, the
population displays several physiological impairments, notable the most
malformed spermatozoa of any population yet described, a recent increase
in the incidence of cryptorchidism, and the abrupt appearance of a lethal
congenital heart defect and heart murmurs (Roelke et al. 1993). In
addition, a score of infectious pathogens has been observed to threaten
the population; even in the face of an aggressive vaccination program.
Concerns over Genetic
Health - Concerns
over genetic health of the Florida panther have surfaced on numerous
occasions since the formation of the Florida Panther Interagency Committee
in 1986. The subject has been the topic of three workshops specific to
the issue in the recent past (May 1991, October 1992 and September 1994).
Experts in the fields of genetics, small population biology, captive
breeding, and panther health, biology, and demographics participating in
these workshops concluded that restoration of gene flow is critical to
restoring genetic health to the panther, to panther survival, and to the
success of the overall recovery program. Because erosion of genetic
health is continuing to occur and could rapidly accelerate at any time,
conclusions at the above referenced workshops has been that a program to
restore genetic health to the Florida panther must be initiated as quickly
as possible.
This Environmental Assessment (EA) is intended to aid in the
decision-making process regarding the development and implementation of a
genetic restoration and management program. Such a program is now
considered essential to the survival and recovery of the Florida panther.
The purpose of this EA is to consider various courses of action that may
be available for genetic restoration and management and to evaluate
environmental impacts that may be associated with the implementation of
these actions. It is not the intent of this assessment to provide a
detailed review or accounting of other tasks that may be important to
panther survival and recovery as called for in the recovery plan. The
importance of other key actions, such as the protection and enhancement of
the wild population and associated habitats, population reestablishment,
captive breeding, etc. will not diminish with the development and
implementation of a genetic management program.
E. Recovery Goal - The
present
recovery objective as stated in the approved recovery plan is to achieve
three viable, self-sustaining populations within the panther's historic
range. Workshops in 1989 to evaluate existing population conditions and
to develop a plan to achieve and maintain population viability for the
panther determined that a total population of 500 breeding age animals
would be needed. It was understood that because landscapes supporting
panther historically had been significantly reduced and fragmented, a
total population goal of 500 breeding age animals would not likely be
achievable at any single population site in the wild. Therefore,
the population goal of 500 would have to be achieved through the
development and management of several sub-populations, both in the wild
and in captivity. Minimum population goals to 50 adult panthers was
established for each wild sub-population. The action proposed herein
would not create any new sub-populations, but, would be expected to result
in improved genetic health of the sole remaining wild population, which is
located in southern Florida. Improved genetic health would provide
enhanced opportunities for success of future population reestablishment
programs.
F. Recovery Thrusts -
The present
Florida panther recovery program places emphases along three major
thrusts: (1) actions to protect and enhance the sole remaining wild
population and associated habitats; (2) actions to manage remaining
genetic resources to improve genetic health; and, (3) actions to identify
population reestablishment sites and develop reintroduction technologies.
G. Genetic
Restoration - Genetic
restoration can be accomplished by reinstating gene flow from western
populations into the Florida population be selectively translocating
individual animals that can be recruited into the population as breeders.
Such a management action seeks to mimic historic gene flow into the
population. The intent is not to replace, or swamp, the F. c.
coryi gene pool with western Felis concolor genes. Rather,
the intent is to reduce occurrence of inbreeding and restore genetic
variability and vitality of offspring produced and recruited as breeders
into a healthier more resilient population of F. c. coryi.
Furthermore, the enhanced genetic variation and gene flow would provide
the necessary genetic material to restore the process of natural selection
to the Florida population. Thus, restoration is intended not only to
reverse the consequences of inbreeding and associated loss of genetic
variation, but also to restore evolutionary adaptive potential of the
Florida population. Recovery of F. c. coryi will be greatly
enhanced by such actions.
H. Intercrossing For Genetic
Restoration - Intercrossing, as used herein, refers to a
mating between subspecies of the same taxonomic species and simulates
integradation which is a common, natural, and expected occurrence in
nature wherever ranges are adjacent. The U.S. Fish and Wildlife Service
(FWS) is presently developing policy to address intercrossing and its
appropriate role and application under provisions of the Endangered
Species Act. The FWS has determined that genetic restoration through
intercrossing can be an acceptable recovery action for the Florida panther
(U.S. Fish and Wildlife Service 1994). However, as part of the
intercrossing program, specific actions would have to be taken and
conditions met. Significant among these are: intercrossing would have to
be scientifically controlled, the genetic profile of the progeny would
have to be specified and most closely resemble the listed species, the
recovery plan would have to be revised to incorporate intercrossing,
compliance with provisions of the National Environmental Policy Act would
have to be achieved, a genetic management plan would have to be developed,
and appropriate studies to ascertain whether environmental contaminants
are contributing to physiological conditions observed in the population
would have to be initiated.
I. Recovery Plan
Revision - The
present recovery plan for the Florida panther, which was last revised in
1987, does not have a task specific to genetic management or restoration.
However, Task 1241 sets the stage for such action. Task 1241 reads:
"Fish and Wildlife Service and Florida Game and Fresh Water Fish
Commissions will identify biological and legal options if the genetic
profile indicates low genetic diversity and subsequent detrimental effects
on the population". To proceed with actions to address "low
genetic diversity and subsequent detrimental effects on the
population", the following revision to the recovery plan is being
undertaken (Federal Register Notice 59[177]:47149, dated September 14,
1994). A new task (Task 12411) is being added to the plan to read:
The Florida Panther Interagency Committee will develop and implement
a management strategy to restore and maintain the historic genetic
character of the Florida panther.
J. Genetic Management
Plan - A genetic
management plan has been developed to guide the genetic restoration
program. The plan, appended as Enclosure I to this document, describes
the biological circumstances (historic and current), alternatives,
implementation strategy, methods, experimental controls, monitoring,
genetic and morphological objectives/profiles, source stock, and short-
and long-term management needs of the proposed genetic restoration
program.