Geographic Range
Black giant squirrels are found across much of the Oriental region. Their native range
spans from northern Nepal and southern China through Vietnam. They are also numerous
across the Malaysian Peninsula (Endo et al., 2004). For this reason they are also
referred to as Malayan giant squirrels.
Habitat
Black giant squirrels are only found in heavily forested areas. Their range spans
from sea level to as high as 2000 m. Since they are highly susceptible to deforestation,
they are rarely found in degraded areas ("Wildlife in Lao PDR: 1999 Status Report",
1999). These squirrels are commonly seen between elevations of 1900 m and 2000 m,
most frequently in areas rich in Vietnamese white pine,
Pinus dalatensis
(Abramov, Rozhnov and Morozov, 2006). Often, they are found nesting in the canopy
of tall trees (Harrison and Traub, 1950).
- Habitat Regions
- tropical
- terrestrial
- Terrestrial Biomes
- forest
Physical Description
Black giant squirrels are characterized by their distinct size and pelage. With masses
of 1546 g and lengths of 798 mm (head to tail), black giant squirrels are one of the
largest members of the
squirrel family
(Thorington and Heaney, 1981). They are identifiable by their black fur, tan chest
patch and occasionally tan tail tip. As is the case with most tree squirrels they
do not exhibit sexually dimorphic. Unlike many squirrels, black giant squirrels do
not have a tail that curls over its back. Instead, their tail lays limp behind them
(Dobroruka, 1975).
- Other Physical Features
- endothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
Reproduction
Mating behavior of black giant squirrels have only been studied with a few select
captive pairs. However, several commonalities have been witnessed. Courtship behaviors
include scent marking, chasing, nest building and grooming. Scent marking involves
both male and females pressing their anogenital region against an object or the ground
and urinating while moving slowly forward (Paulraj, 1988). Chasing involves males
pursuing the female while she runs and hides. Often, this gives less dominant males
a chance to find her before they can be chased off by older males (Thorington and
Ferrell, 2006).
The mating systems for black giant squirrels in the wild have not been well studied.
However, like many other solitary tree squirrels it is known to be polygynandrous
(Dobroruka, 1975). Similar Malaysian tree squirrels are also polygynandrous. Their
mating systems are assumed to reflect those of close relatives,
Indian giant squirrels
. For other close relatives,
plantain
and
gray-bellied squirrels
, when a female comes into estrous, six to eight males will come to the area early
in the morning. During a several hour mating bout, five to seven males will copulate
with the female. Males frequently attempt to chase off other males when in close proximity
to the female (Tamura, 1993). Since several males will copulate with the female, it
is not uncommon for siblings of the same litter to have different paternity (Thorington
and Heaney, 1981). Squirrels that inhabit similar ecological or energetic niches also
have similar mating and reproductive systems (Hayssen, 2008).
- Mating System
- polygynandrous (promiscuous)
Black giant squirrels exhibit very similar reproductive behavior to most tree squirrel
species. A female will give birth to one to two altricial young twice yearly. They
have a gestation period that lasts an average of 31.5 days. After which, they will
nurse their young for approximately five weeks. Like all members of the
squirrel family
, black giant squirrels reproduce sexually with the male impregnating the female during
internal copulation. The reproductive efforts of all tree squirrel species take place
in the canopy layer. This includes both nesting and mating efforts (Hayssen, 2008).
Black giant squirrels give birth in two periods, from April to May and August to September
(Hayssen, Tienhoven, and Tienhoven, 1993).
- Key Reproductive Features
- iteroparous
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- viviparous
Black giant squirrels give birth to altricial young that must be nursed; mothers provide
this in the form of lactation. Males are only present for insemination and do not
aid in parental care (Harrison and Traub, 1950). No evidence suggests that the young
remain with the mother after they are weaned.
- Parental Investment
- altricial
- female parental care
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- female
-
provisioning
Lifespan/Longevity
The average lifespan for black giant squirrels is 18 years in captivity. There are
very few records detailing the lifespan of black giant squirrels all of which have
been collected from captive, wild-born specimens.
Behavior
Black giant squirrels are diurnal and known for their tendency to make its nests in
the canopy of tall trees (Harrison and Traub, 1950). Like most tree squirrels they
are a solitary animals, although they occasionally are seen in groups or pairs during
the breeding season. Black giant squirrels do not form hierarchical groups (Dobroruka,
1975). Unlike ground squirrels, tree-living species do not hibernate. All tree species
of squirrels (including black giant squirrels) are active during all parts of the
year (Thorington and Ferrell, 2006).
Home Range
Black giant squirrels will forage on the ground for fruit and nuts extending their
range below their normal habitat in the canopy (Meijaard and Sheil, 2008). However,
the size of their home range is not known.
Communication and Perception
The specific communication systems of black giant squirrels have not been studied
thoroughly. However, they likely communicate in much the same way as other members
of the
squirrel family
. This means that they communicate through a series of vocal chirps and barks. In
other Malaysian squirrel species, communication plays a large role in mating systems.
Males locate and attract females using ultrasonic sounds. They will also bark post
copulation for several minutes (Tamura, 1993). When courting, both genders will scent
mark using urination to attract members of the opposite sex and show availability
(Paulraj, 1988). As with many
squirrels
, they use alarm calls when they see a predator (Thorington and Ferrell, 2006).
- Other Communication Modes
- scent marks
Food Habits
Like most squirrels, black giant squirrels eat fruits and nuts. Little is known about
their foraging activity and the amount of food they consumes (Meijaard and Sheil,
2006). Locals within its range insist that they frequent their orchards (Harrison
and Traub, 1950).
- Plant Foods
- seeds, grains, and nuts
- fruit
Predation
Black giant squirrels are preyed upon by several species. They live in the upper canopy,
which allows them to avoid many ground predators (Harrison and Traub, 1950). However,
this puts them at risk of predation from birds of prey such as
Wallace's hawk eagle
, which preys on arboreal mammals in Southeast Asia (Haring et al., 2007). Black giant
squirrels are also at risk of predation by
snakes
when in the canopy. In order to collect food on the forest floor, they will occasionally
move down from the canopy (Meijaard and Sheil, 2008); during which they are at risk
of predation from terrestrial carnivores. However, the specific species that eat black
giant squirrels have not been thoroughly studied.
Black giant squirrels have several means of predator avoidance. As mentioned before,
the location that they live in is out of reach of many terrestrial predators (Harrison
and Traub, 1950). Also, as with many
squirrels
, they will use alarm calls when they see a predator. Their fur also provides camouflage,
similar to many other
squirrels
. The ventral, or belly is a light color, while the dorsal, or back remains dark.
This helps them blend in with the changing light patterns of the forest layers and
avoid being seen from both terrestrial and aerial predators (Thorington and Ferrell,
2006).
- Anti-predator Adaptations
- aposematic
- cryptic
Ecosystem Roles
Because of their affinity for fruit and nuts black giant squirrels disperse seeds
of large-seeded tree species. More specifically, these squirrels are known to disperse
Burseraceae seeds (
Canarium euphyllum
; Kitamura et al., 2006).
- Ecosystem Impact
- disperses seeds
- Burseraceae trees ( Canarium euphyllum )
Economic Importance for Humans: Positive
Black giant squirrels were, until recently sold in large quantities at fresh food
markets in Vientiane, Loas. At the time, they were one of the most commonly found
specimens in several markets. In recent years, they are not as abundant in these markets
due to declining wild populations ("Wildlife in Lao PDR: 1999 Status Report", 1999).
- Positive Impacts
- food
Economic Importance for Humans: Negative
Black giant squirrels have been known to steal fruit from local orchards. (Harrison
and Traub, 1950)
- Negative Impacts
- crop pest
Conservation Status
Black giant squirrels are susceptible to hunting and deforestation. they are in decline
mainly due to over-hunting and secondarily due to habitat loss (Timmins and Duckworth,
2008). Historically, they have been sold in fresh food markets in Loas ("Wildlife
in Lao PDR: 1999 Status Report", 1999). Black giant squirrels are significantly less
abundant or not present in logged forests and plantation areas. This reduction in
number is strongly correlated to the reduction in canopy cover and tree density (Datta
and Goyal, 2008), because black giant squirrels nest in the high canopy layer of tall
trees (Harrison and Traub, 1950).
Additional Links
Contributors
Michelle Sutton (author), University of Alaska Fairbanks, Laura Prugh (editor), University of Washington, Laura Podzikowski (editor), Special Projects.
- oriental
-
found in the oriental region of the world. In other words, India and southeast Asia.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- terrestrial
-
Living on the ground.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- polygynandrous
-
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- altricial
-
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
- female parental care
-
parental care is carried out by females
- arboreal
-
Referring to an animal that lives in trees; tree-climbing.
- diurnal
-
- active during the day, 2. lasting for one day.
- motile
-
having the capacity to move from one place to another.
- solitary
-
lives alone
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- scent marks
-
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- aposematic
-
having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.
- cryptic
-
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
- food
-
A substance that provides both nutrients and energy to a living thing.
- herbivore
-
An animal that eats mainly plants or parts of plants.
- frugivore
-
an animal that mainly eats fruit
- granivore
-
an animal that mainly eats seeds
- endothermic
-
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
References
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