John
R. Meyer, Ph.D.
September 1994
During my travels throughout Belize, I have occasionally
encountered reports and rumors regarding the occurrence
of the black, or melanistic, phase of the jaguar, Panthera
onca, in Belize. During 12 years spent as a staff member
at the Jacksonville Zoo in Jacksonville, Florida, I had
the opportunity to be involved with a breeding program that
produced both black and spotted phases of the jaguar. As
an outgrowth of my interest in elucidating the genetics
of melanism in this cat, I undertook a survey of the occurrence
of this phenomenon in the wild, a project that revealed
some interesting facets of the distribution and occurrence
of melanism in wild jaguars.
Jaguars have been maintained in captivity for several
centuries, going back to at least the early 1500's, when
they were reported in the emperor Montezuma's collection
in what is now Mexico City (Diaz, 1956). From that time
until the middle of the present century, captive breeding
was sporadic, as it was a relatively easy matter to acquire
replacement animals from the wild. By the early 1970's,
when serious conservation efforts were initiated with the
Endangered Species Act (ESA) and the Convention on International
Trade in Endangered Species (CITES), the reproduction of
jaguars in zoos was well-established and the captive population
self-sustaining.
There occurs in jaguars, as well as in leopards (Panthera
pardus), a melanistic phase which has been much sought
by zoos for exhibition purposes. This color phase was relatively
difficult to acquire until the 1970's, by which time a few
zoos, among them the Jacksonville Zoo, had begun to breed
them regularly. Until this time, it had been assumed that
the black phase of the jaguar, as is the case for the leopard,
was the result of a recessive genetic trait. By the late
1970's, it had been demonstrated conclusively that melanism
in jaguars is a result of a dominant allele (Deutsch, 1975;
Dittrich, 1979); in spite of this documentation in the literature,
the phenomenon was not widely recognized throughout the
research community until the late 1980's. Mondolfi and Hoogesteijn
(1982) considered melanism in jaguars to represent a recessive
condition, and several field biologists (Robin Best, in
litt.; Russell Mittermeier, in litt.; Alan Rabinowitz, in
litt.) expressed surprise upon learning from the author
that the opposite was true. One probable reason for this
misconception, in addition to the situation with leopards,
is the fact that the melanistic phase does not occur throughout
a large portion of the jaguar's range, and where it does
occur it is usually with a lower frequency than the spotted
phase (Nowak, 1991). Most of the large cats have extensive
geographical distributions, and the jaguar is no exception.
Its range has shrunk somewhat in the past century due to
man's persecution, but historically the jaguar was found
from the southwestern U.S. through Mexico and Central America
to South America, where it was widespread east of the Andes
and south as far as the Argentine pampas (Guiggisberg, 1975;
Nowak, 1991). Since jaguars in general are secretive, reliable
reports of melanistic individuals are difficult to acquire,
particularly from the literature. Without doubt, Brazil
has the largest population of black jaguars, not surprising
since this country contains the largest remaining wilderness
area in the jaguar's range. Melanistic individuals have
been reported from the following states of Brazil: Amazonas
by Bates (1892) and Almeida (1976); Para by Smith (1976),
E. Im Thurn, 1883 (cited in Perry, 1970), Shoumatoff (1978),
Almeida (1976), and Sick (1961); Rio Branco by Shoumatoff
(1978); Mato Grosso by Roosevelt (1926) and Wavrin (1936);
Minas Gerais by L.A. Deutsch (in litt.), Russell Mittermeier
(pers. comm.), and Almeida (1976); Goias by L.A. Deutsch
(in litt.).
Elsewhere in South America, black jaguars have been reported
from Venezuela (Humboldt, 1853; Mondolfi and Hoojesteijn,
1982), Guyana, R. Schomburgk, 1922 (cited in Perry, 1970),
Ecuador (Wavrin, 1936), Peru (Wavrin, 1936; Poeppig, 1835;
J. von Tschudi, 1847 (cited in Perry, 1970); John Terborgh,
in litt.), and Paraguay (Rengger, 1830). The Jacksonville
Zoo had a wild caught male that was shipped from Leticia,
Colombia, but could have originated from nearby Brazil or
Peru, as well as Colombia. Upon its death, this male was
deposited in the collection of the Florida Museum of Natural
History. Although no literature records have been encountered,
it is likely that melanistic individuals occur in the South
American countries of Suriname, French Guiana, and Bolivia,
particularly in those areas in or adjoining the Amazon basin.
Outside of South America, the only published report of
melanism encountered was that of Perry (1970), who stated
that A. Verrill found black jaguars greatly feared by the
Indians in Costa Rica. Christopher Vaughan reported (in
litt.) that there have been several reported sightings in
Costa Rica, but there are no specimens to substantiate these
claims. Following his two year study of jaguars in Belize,
Rabinowitz (1986) stated that there were probably no black
jaguars in that country, although Sharon Matola of the Belize
Zoo indicated to the author that she has seen what appeared
to be a melanistic jaguar in Belize. In spite of persistent
reports of black jaguar sightings (Jan Meerman, pers. comm.),
my own investigations and experience in Belize lead me to
agree with Rabinowitz, particularly given the lack of documented
records for the nearby countries of Mexico, Guatemala, and
Honduras. In the absence of any other indication of melanism
in Central America or Mexico (Leopold, 1959), a region relatively
well-explored biologically, it seems reasonable to state
that black jaguars do not occur outside of South America,
and more specifically, not beyond the northern periphery
of the Amazon basin in Colombia. Nevertheless, it is not
impossible that isolated populations might contain the allele
for melanism, and certainly Belize, with its relatively
large jaguar population, warrants further examination.
No scientific study has yet been undertaken in any part
of the black jaguar's range to determine its abundance with
respect to the spotted phase. Smith (1976) stated that the
unspotted cats (including melanistic jaguars) have little
commercial value in the illegal Amazon skin trade, so a
survey of that activity would probably not reflect the relative
abundance. A survey on the status of the jaguar (Swank and
Teer, 1987) contains no information on the spotted versus
the melanistic phase. The anecdotal evidence indicates that
there is a wide range of incidence of melanism in jaguars,
ranging from uncommon to frequent, and there appears to
be a possible geographic trend in this incidence. The uneven
incidence of the melanistic phase of the jaguar in the wild
raises some interesting questions, not the least of which
is how it came to its present apparent pattern of distribution.
Three categories of factors suggest themselves as possible
elements in the development of the observed situation. It
may prove to be that only one of these factors is responsible,
or a combination of several factors may be the directing
force.
Genetic factors may be operating to limit the frequency
of the black morph in the wild, although at present there
is no evidence suggesting how this may operate (Rabinowitz,
1986). Robinson (1970), in a study of melanism in leopards,
discovered what appeared to be a reduction in litter size
in matings involving two black individuals, but in this
case the melanism is a recessive trait. The data available
from captive breeding of jaguars (Dittrich, 1979; Deutsch,
1981; pers. observ.) give no indication that there is any
difference in litter size in pairings involving two blacks,
two spotteds, or black with spotted crosses. Robinson (1970)
further noted that in certain areas, particularly the forests
of southeast Asia, the black phase of the leopard may outnumber
the spotted phase, and he suggested that if the disadvantage
associated with reduced litter size in black leopards operates
in the wild, it may be a factor in the maintenance of the
spotted/black dimorphism. The failure of the black phase
to completely displace the spotted could depend on this
aspect. An analogous system, as yet unsuspected, may be
operating in the case of the jaguar, responsible for the
maintenance of a dimorphic color pattern. It is interesting
to speculate that there could be some selective disadvantage
(even lethal) in the homozygous dominant condition in black
jaguars, but the data on matings of two blacks are too limited
to show evidence of reduced viability. It does appear from
what evidence is available involving crosses of black with
spotted jaguars (Dittrich, 1979; pers. observ.) that most,
if not all, of the black parents were heterozygous for the
color alleles.
Another set of factors that may have determined the present
distribution and abundance of black jaguars may be termed
historical, referring in this case to the geologic and climatic
history of the American continents. Simpson (1980) stated
that "the jaguar or its immediate ancestor evolved
in Asia and spread through both the Americas without further
radiation". He further indicated that jaguars are known
from fossils in South America from the middle Pleistocene
(Ensenadan) onward. Fossil evidence shows that the species
occurred in Florida as recently as 7000 to 8000 years ago
(Martin and Webb, 1974), and Guggisberg (1975) felt that
it may have been encountered as far north and east as southern
Louisiana in recent times. Unfortunately, there is no way
at present to determine from the fossil material what the
color pattern of these early jaguars was, so an analysis
of the effects of past climatic and geologic change has
to be based on indirect evidence.
In recent years, an increasing body of knowledge has become
available on the geologic and climatic history of Central
and South America. For the jaguar, the Pleistocene history
is of greatest potential significance, and some of what
is now known or hypothesized concerning this time period
is of interest. Several authors (Haffer, 1979; Duellman,
1979; Simpson, 1979; Lynch, 1979; Dixon, 1979; Dixon and
Rivero Blanco, 1979) have summarized much of the data concerning
the Pleistocene biogeography of South America, and the evidence
presented indicates that there are several historical possibilities
that could account for the present apparent distribution
and frequency of the black jaguar. Unfortunately, not enough
hard evidence is presently available regarding the incidence
of the melanistic phase to make it worth speculating on
the possible effects of Pleistocene climatic fluctuation.
However, it does seem that if the pattern of distribution
and frequency as it presently appears should prove to be
real, the past climate and its resultant ecologic changes
will probably provide the best hypothesis to explain the
phenomenon.
The final set of factors that may have some bearing on
the determination of the present distribution of melanistic
jaguars may be termed ecologic. This can include all manner
of biological relationships, ranging from prey species to
habitat types, and almost certainly some have had roles
in influencing the evolution of the jaguar.
Throughout its entire range, the jaguar is known to inhabit
a wide variety of habitat types, and has been recorded at
elevations ranging from sea level to almost 3000 meters
(Guggisberg, 1975; Perry, 1970). Most observers and researchers
seem to feel, however, that the optimum habitat for jaguars
is the wetter lowland areas, with vegetation ranging from
mixed savanna to rainforest (Mondolfi and Hoogesteijn, 1982;
Guggisberg, 1975; Thornbeck and Jenkins, 1982). In the long
term evolutionary history of the jaguar, it may have been
this optimum habitat and its fluctuating history that has
had the greatest influence upon the development of the present
distribution pattern. Of the black phase, very little is
known regarding optimum environmental conditions, but the
impression gained from the distribution records is that
it is primarily an animal of rainforest areas. Certainly
a tempting hypothesis is that the melanistic form is difficult
for prey to see in the darkened rainforest, and this may
eventually prove to be the case. It should be pointed out,
however, that within the range of the jaguar there are,
or historically were, areas of fairly extensive rainforest
within which black jaguars do not occur. It is likely that
the ultimate explanation for the uneven distribution of
the black morph will involve several factors, such as fluctuating
climate and rainforest distribution, which may have resulted
in its absence in Central America and Mexico.
Until field studies are undertaken of a population with
a high incidence of melanistic individuals, it is futile
to speculate further on the relative importance of various
factors, be they genetic, ecologic, or historic. There is
also a great need for additional field studies of populations
throughout the range to develop a better understanding of
the variation in the ecology of this widespread species,
especially given the ever-shrinking range of the species.
Belize, with its relatively large population of jaguars
and the prospect for their continuing existence, presents
an ideal situation for more detailed field studies, and
data gathered in these studies would be of great comparative
value with data gathered from populations containing melanistic
individuals in South America. It will also be of great value
for Belizean biologists, naturalists, and protected area
personnel to report all jaguar sightings to a centralized
data center so that reliable information on jaguar distribution,
frequency, and pattern can be evaluated.
|
Latest
report: This
black jaguar was reportedly killed in Belize (then British
Honduras) in the early 70's. The people who helped with
the dogs had no idea that the cat was in the area and
were, reportedly, terrified that the spirit of the animal
would hunt them. The outfitter seemed to believe that
black cats were rare because the mother cats would kill
the "different" kit. It is still on the mount
today |
Literature Cited
Almeida, A. 1976. Jaguar hunting in the
Mato Grosso. Stanwill Press, London.
Bates, H.W. 1892. A naturalist on the River
Amazon. London.
Deutsch, L.A. 1975. Contribuicao para o
conhecimento do Panthera onca (Linne) - onca pintada (Mammalia-Carnivora).
Cruzamento de exemplares pintadas com melanicos. Ciencias
Biol., Secao 5, Zoologica H.5: 369-370.
_______. 1981. Contribuicao para conhecimento
da Panthera onca (Linne) - onca pintada (Mammalia-Carnivora).
Cruzamento de exemplares pintadas com melanicos. IV Reuniao
da Sociedade de Zoologicos do Brasil.
Diaz, Bernal. 1956. The discovery and conquest
of Mexico. Farrar, Straus and Cudahy, New York.
Dittrich, L. 1979. Die vererbung des melanismus
bein jaguar (Panthera onca). Zool. Garten N.F., Jena 49(6):
417-428.
Dixon, J. 1979. Origin and distribution
of reptiles in lowland tropical rainforests of South America.
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origin, evolution, and dispersal. Univ. Kansas Mus. Nat.
Hist., Monograph 7: 217-240.
Duellman, W. 1979. The herpetofauna of the
Andes: Patterns of distribution, origin, differentiation,
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American herpetofauna: its origin, evolution, and dispersal.
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Duguid, J. 1932. Tiger-man. National Travel
Club, New York.
Guggisberg, C. 1975. Wild cats of the world.
David and Charles, Newton Abbot, London.
Haffer, J. 1979. Quaternary biogeography
of tropical lowland South America. In Duellman, W. (ed.).
The South American herpetofauna: its origin, evolution,
and dispersal. Univ. Kansas Mus. Nat. Hist., Monograph 7:
107-140.
Humboldt, A. von. 1853. Personal narrative
of travels to the equinoctal regions of
America during 1799-1804. London.
Leopold, A.S. 1959. Wildlife of Mexico.
Univ. Calif. Press, Berkeley, 568 p.
Lynch, J. 1979. The amphibians of the lowland
tropical rainforests. In Duellman W. (ed.).
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Martin, R. and S. Webb. 1974. Late Pleistocene
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(ed.) Pleistocene mammals of Florida. Univ. Florida Press,
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Mondolfi, E. and R. Hoogesteijn. 1982. Biology
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World. (5th ed.), Vol. II. Johns Hopkins Univ. Press, Baltimore,
1629 p.
Perry, R. 1970. The world of the jaguar.
Newton-Abbot, New York.
Poeppig, E. 1835-36. Reise in Chile, Peru
und auf den Amazonenstrome waehrend der jahre 1827-32. Leipzig.
Rengger, J. 1830. Naturgeschichte der saugerteire
von Paraguay. Basel.
Rivero-Blanco, C. and J. Dixon. 1979. Origin
and distribution of the herpetofauna of the dry lowland
regions of northern South America. In Duellman, W. (ed.)
The South American herpetofauna: its origin, evolution,
and dispersal. Univ. Kansas Mus. Nat. Hist., Monograph 7:
281-298.
Robinson, R. 1970. Inheritance of the black
form of the leopard, Panthera pardus. Genetica 41: 190-197.
Roosevelt, T. 1926. Through the Brazilian
wilderness. Schribner's, New York.
Shoumatoff, A. The Rivers Amazon. Sierra
Club Books, San Francisco.
Sick, H. 1961. Tucani. Editorial Labor,
Barcelona.
Simpson, B. 1979. Quaternary biogeography
of the high montane regions of South America. In Duellman,
W. (ed.) The South American herpetofauna: its origin, evolution,
and dispersal. Univ. Kansas Mus. Nat. Hist., Monograph 7:
157-188.
Simpson, G. 1980. Splendid isolation. The
curious history of South American mammals. Yale Univ. Press,
New Haven.
Smith, N. 1976. Spotted cats and the Amazon
skin trade. Oryx 13(4): 362-371.
Swank, W. and J. Teer. 1989. Status of the
jaguar - 1987. Oryx 23: 14-21.
Thornbeck, J. and M. Jenkins (ed.). 1982.
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Wavrin, Marquis de. 1939. Les betes sauvages
de l'Amazonie. Paris.
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