Black Giant Squirrels

Black Giant Squirrel (Ratufa bicolor)

A Google search will show the Black Giant Squirrel is the biggest squirrel species on our planet. It may not be the prettiest as it has to contend with the Indian Giant Squirrel (or Malabar Giant Squirrel)..Ratufa Indica...that comes in multi-colours.

Indian Giant Squirrel (Ratufa indica)

    DISTRIBUTION

The Black Giant squirrel or Malayan Giant squirrel (Ratufa bicolor) is a large tree squirrel in the genus Ratufa native to the Indomalayan zootope. It is found in forests from Northern Bangladesh. northeast India, Thailand, Malaysia, eastern Nepal, Bhutan, southern China, Myanmar, Laos, Cambodia, Vietnam and western Indonesia (Java, Sumatra, Bali and nearby small islands.

DESCRIPTION

The Black Giant squirrel is one of the largest species of squirrel in the world. On average, an adult Black Giant squirrel weighs round 1-05-1-25 kg (2.3-2.8 lb), has a head plus body length of 34-37cm (13-15in) and the tail is 41-42 cm (16-17in) long.

The species is typically distinctly bicoloured with dark upper-parts and pale under-parts. The back, top of the head, ears, and bushy tail are deep brown to black and the underparts are light-buff-coloured. On the small islands of Myanmar and in the Strait of Malacca the Black Giant Squirrel has reddish yellow underparts. As is the case with most tree squirrels they are not sexually dimorphic. Unlike many squirrels, Black Giant squirrels do not have a tail that curls over the back. Instead, their tails lay limp behind them somewhat like the Dusky Langurs. Both species use their tail for balance while leaping or climbing.

All the observations and photographs in this article are from this species in a forest on the north side pf Penang Hill (near Pearl Hill).

There is no size comparison but this is a juvenile, about half the size of an adult

HABITAT

Ratufa bicolor's range includes a variety of bioregions that share the commonality of being forested. It ranges in elevation from sea level up to at least 1400 metres (4,600ft). in some of the most rugged land in the world. However, in recent decades, R. bicolor's habitat has been steadily encroached upon by human settlement, timber harvesting, and agriculture, which along with overhunting by human predation in parts of its range, has resulted in a total loss of 30% of the population in the last 10 years. In the tropical rainforest of the Malay Peninsula and Indonesia, R. bicolor is not as abundant as elsewhere in its range, which is probably due to competition from other arboreal species (especially primates) for food in the upper forest canopy. This is certainly the case in the study area as they compete directly with Dusky Langurs. These squirrels are rated as 'Near threatened'.

Part of the study area, adjacent to Diamond Villa 

BEHAVIOUR & DIET

R. Bicolor is diurnal and arboreal, but sometimes climbs down from the forest canopy to feed on the ground. The species is rather reclusive and rarely enters plantations or settlements

Its diet consists of seeds, fruit and leaves. It is primarily solitary.

In the adjacent forest the Black Giant squirrels can be seen readily while they are nest building or feeding on their favourite foods. There are a 4 acacia trees and when they are producing the seeds the squirrels are frequent visitors, as seen in the images below.. They have competition from Dusky Langurs and Plantain Squirrels for this favourite food.

The Acacia tree seeds are also very popular with the Dusky Langurs (with 10 of them in the picture below)

NEST BUILDING

A squirrel pair will have multiple nests (dreys). The male appears to be the main constructor although he is assisted by the female at times. They bite off the end of branches and stack them firmly at the junction of several branches. They will add to the structure weeks later. The attached leaves die off but the structure appears wind resistant and is apparently waterproof.  Conventional wisdom has it that one is the home while others are for sleepovers. Another theory is that some are dummy nests to fool predators. I have not seen any of the eight nests under observation, being slept in or lived in and most resident raptors would not be fooled by dummy nests. 

Comparing the nest size with the size of a Dusky Langur

COMMUNICATION

The associate Plantain Squirrels communicate vocally with each other regularly, especially when alarmed. The Black Giant squirrels make sounds infrequently. Other species communicate with chirps and barks and can communicate using ultrasonic sounds. Despite an intensive search I have not found recordings of Black Giant squirrels. There is an interesting recording of a related Malaysia species here.

SHARING THE HABITAT

    

There appears to be defined routes through the forest and these are common to the squirrels and the langurs. The images below show Squirrels and Langurs both using a Fishtail fern bridge.

As mentioned, the local Black Giant Squirrels share their domain with Dusky Langurs. They compete for a variety of foods but otherwise have a peaceful existence.  The squirrels are elusive and secretive and the Langurs are usually non-aggressive. Both love eating the seed pods from Acacia trees and several times I have seen them together on a tree. On one occasion the Langur seemed to tease the squirrel but deliberately cutting off its escape. The squirrel was gone in a flash and dived off the tree, much to the apparent mirth of a langur witness.

The domain is also shared with the much smaller Plantain Squirrel, Long-tailed Macaques, Clouded Monitor lizards and fruit-eating birds such as Pink-necked Green Pigeons that will compete for fruit.

Dusky Langur and Black Giant Squirrel on the same tree

Black Giant Squirrel and Clouded Monitor Lizard on the same tree

Plantain Squirrel

Clouded Monitor Lizard

Long-tailed Macaque

Pink-necked Green Pigeon (male)

REPRODUCTION

Courtship behaviour includes scent marking, chasing, nest building and grooming. Scent marking involves both males and females pressing their anogenital region against an object or the ground and urinating while moving slowly forward.

Black Giant squirrels exhibit very similar reproductive behaviour to most tree squirrel species. A female will give birth to one or two young twice yearly. They have a gestation period of 31.5 days. After which, they will nurse their young for approximately five weeks. Reproduction takes place in the canopy region and includes nesting and mating.The species give birth in two periods, from April to May and August to September. The young are weaned in 5 weeks and they are independent after this period. The male takes no part in the process after insemination. 

The terminology for the adults are buck and doe and the young are kittens.

In the forest fragment under observation I have no idea where the active nest is and I have not seen small kittens...so they do a good job at remaining secretive and giving the young a good survival chance.

New born squirrels are born blind and naked but with claws (ouch) and progress rapidly with their mothers milk.

Newborn

Three months old

PREDATION

Black Giant squirrels are preyed upon by several species, They live in the upper canopy, which allows them to avoid ground predators. However, this puts them at risk of predation from birds of prey such as Wallace's Hawk Eagle, which is known to prey on arboreal mammals in Southeast Asia. Black Giant squirrels are also at risk of predation from snakes, especially large snakes, such as pythons that can also be a problem for Dusky Langurs. In the rainforest under study a number of raptors have been identified: White-bellied Sea Eagles, Brahminy Kites, Crested Serpent Eagles and  Changeable Hawk-eagles, both the light and dark morphs.

The adult Black Giant squirrels are unlikely victims of any of the raptors but the kittens would be vulnerable to attack, as are the smaller Plantain Squirrels

Undoubtedly the worst predator is man. In Laos several decades ago the Black Giant squirrels were the most abundant food item from the forest in a number of markets. This has only declined as the numbers have declined.

Juvenile White-bellied Sea Eagle

Adult White-bellied Sea Eagle

Brahminy Kite

Changeable Hawk Eagle (dark morph)

Crested Serpent Eagle

PHYSICAL ATTRIBUTES

Despite their increased size the Black Giant squirrels are very active and agile. They take long leaps from treetop to treetop with ease. Like the Dusky Langurs they will also take daredevil leaps into a treetop tens of metres below. When leaping from trees they seem to be able to compress their bodies into a more aerodynamic shape.

It is interesting to compare the disposition of the tail in the Black Giant squirrel and the Dusky Langur. The tail is up early in the jump but down on arrival at target.

In conclusion:

The only thing I don't understand about this species is; what are all the nests for?