A Very Short Introduction to the Rats, Mice, Shrews, Squirrels & Gerbils of Sri Lanka

Small But Plentiful

There is little submissive, or demure about how Sri Lanka’s smaller mammalian world – its rodents, and rodent-like cousins: its rats, shrews, mice, and squirrels - live their lives. Bottom of the pyramid of mammals they may be, but numbering over 30, they make up not just over a quarter of the island’s land living mammal species, but fifty percent of its endemic species too. To know them, is to know a key part of what really makes Sri Lanka Sri Lankan.


Rats

Two of the island’s ten rat species are endemic. Thirty centimetres in length, nose to tail, with steel grey fur and white undersides, the Ohiya Rat is named after a small village of barely 700 souls near Badulla. It lives quietly in forests and has gradually become ever scarer in counts done by depressed biologists. Its only other endemic cousin, the Nillu Rat, is no less endangered, and today is only found in restricted highland locations such as the Knuckles, Horton Plains, Nuwara Eliya, and Ohiya. Little more than thirty nine centimetres length nose to tail, its fur tends to be slightly redder than the typical grey of many of its relatives. Its name – Nillu, which means cease/settle/ stay/stand/stop - gives something of a clue about its willingness to get out and about.

To these two are joined an embarrassment of other rat species, many common throughout the world, others restricted to South and Southeast Asia, and all much more successful in establishing an enduring if unattractive dominance. These include the massive Greater Bandicoot Rat and its slightly smaller cousin the Lesser Bandicoot Rat. Measuring almost sixty centimetres in length nose to tail, the Greater Bandicoot Rat lives right across South and Southeast Asia and for obvious reasons in known in Sri Lanka as the Pig Rat. Aggressive, highly fertile, widespread, happy to eat practically anything and an enthusiastic carrier of many diseases, it is not the sort of creature to closely befriend. A marginally smaller giant of the rat world is the Lesser Bandicoot Rat, coming in at 40 centimetres length nose to tail. It is found in significant numbers throughout India and Sri Lanka and its fondness for burrowing in the farmlands and gardens its prefers to live within, has earnt it a reputation for destruction. It can be aggressive and is a reliable host to a range of nasty diseases including plague, typhus, leptospirosis, and salmonellosis.

The Black Rat or Rattus Rattus lives in all parts of Sri Lanka and comes in at least five distinct sub species - the Common House-Rat Rat , the Egyptian House Rat, the Indian House Rat, the Common Ceylon House Rat, and the Ceylon Highland Rat. None are much longer than thirty three centimetres nose to tail and despite their reputation for being black, also sport the occasional lighter brown fur. It is phenomenally successful, calling almost every country in the world its home, including Sri Lanka. It is also a disconcertingly resilient transmitter for many diseases, its blood giving a home to a large quantity of infectious bacteria – including the bubonic plague.

Three others tend to restrict themselves more to South Asia - Blanford's Rat, the Indian Bush Rat, and the Indian Soft-Furred Rat
Indeed, Blanford's Rat, known also as White-Tailed Wood Rat, is found in impressive numbers throughout India, Sri Lanka, and Bangladesh. Measuring thirty five centimetres in length nose to tail, it has the classic grey fur of the kind of rat that scares most people. The Indian Bush Rat is also found widely across Sri Lanka and India. It even boasts a tiny pocket sized colony in Iran. At twenty five centimetres in length nose to tail, it is smaller than many other rats and has rather beautiful fur that is speckled yellow, black, and reddish as if it had wandered out of a hair salon having been unable to make up its mind about what exact hair dye ask for, opting instead for a splash of everything. The ultimate C List celebrity, the beautiful Indian Soft Furred Rat is more than happy to make its home at any altitude and almost any place from India, Nepal, and Pakistan to Sri Lanka. So ubiquitous and successful is it, that it lists as being of no concern whatsoever on the registers of environmentalists troubled by species decline. Barely 30 centimetres nose to tail, it has brown to yellow fur on its back and white across its tummy.

The devil of the rat world is undoubtedly the Brown Rat, which boasts a wide range of alterative names all associated either with Lucifer, Satan, Abaddon, Beelzebub, or streets, sewers, or wharfs. Immortalized by Dickens, it has been studied and domesticated more than most mammals and inhabits almost every continent of the world – not least Sri Lanka. It is large – over 50 centimetres nose to tail. It is happy to consume almost anything, is highly social, produces up to 5 litters a year and - according to the more informed scientists, is capable of positive emotional feelings. A final rat, Tatera Sinhaleya, known only from fossil records bade farewell to the island many thousands of years ago.


Mice

Of Sri Lanka’s seven mouse species, nearly half are also endemic. These three native and patriotic rodents is headed by the ultra-rare Sri Lankan Spiny Mouse. It is now so endangered that it can be seen in a few locations. A mere maximum of 18 centimetres length, from nose to tail, its reddish grey back, and sides morph into white underparts, with huge, gorgeous smooth scooped out ears that stand like parasols above large dark eyes. It is a mouse to fall in love with.

The similarly and somewhat confusingly named Mayor’s Spiny Mouse also inhabits the smaller end of the mouse spectrum and comes in two (still quite widespread) variants – Mus Mayori Mayori, which inhabit the hill country; and Mus Mayori Pococki which prefers the low wetlands. Telling them apart is almost impossible, and both are covered with reddish grey fur and exhibit rather unsatisfactorily small ears. Seeing them is also a challenge for they are both nocturnal creatures. One of their more interesting (albeit worrying) points of mouse difference is their capacity to carry quite so many other creatures on them: from mites, ticks, and sucking louses to small scorpions.

The last of the endemic mice is the Ceylon Highland Long tailed Tree Mouse. Discovered in 1929 by the Dutch tea planter, Adriaan Nolthenius, it is an increasingly rare creature, little more than 21 centimetres in length, nose to tail. It is found in Sri Lanka’s hill country where it lives in trees, venturing out only by night. Like most mice, it has reddish brown fur, that occasionally grows darker but compared to its many cousins, presents somewhat disappointingly small ears.

These tiny patriotic native creatures are joined by a range of other mice typically found in other parts of South and South East Asia including the fetching Indian Field Mouse. Measuring a tiny 13 centimetres in length, nose to tail, the Indian Field Mouse is one of those mammals of the Indian subcontinent that has long term residency rights in Sri Lanka where it is found almost everywhere. It is all a mouse aims to be, with a small rounded hunched body, lovely rounded smooth ears, and light brown to white fur.

The almost domesticated Indian House Mouse is a mouse beloved of mouse pet owners, science and, regrettably, is regularly used in laboratories. It is widely distributed across Asia and elsewhere and in urban areas it has become an almost tame companion to the humans its lives around. Rarely more than 20 centimetres in length, nose to tail, it is one of the world‘s most studied and understood mammals, its typical behavioural characteristics itemized even down to the differences exhibited if it lives in sandy dunes rather than an apartment.

The Indian Long-Tailed Tree Mouse is notable for playing host to an especially undesirable tick. Also known as the Indian Long Tailed Climbing Mouse, it is common throughout South and Southeast Asia. It grows to little more than twenty centimetres in length, nose to tail, and sports reddish brown fur that fades to white on its underparts. It is widely distributed – but not a creature to go out of your way to befriend for it is notorious for spreading the tick-borne viral Kyasanur Forest Disease that causes headaches, chills, muscle pain, and vomiting and can take months to recover from.

The final mouse on the island is the rather clumsily named Ceylon Field Mouse, whose home actually stretches from Sri Lanka to Cambodia. It happily populates almost all kinds of habitats. It is often called the Fawn Colour Mouse for its light fur and grows to little more than 15 centimetres in length, nose to tail.


Shrews

Of the ten shrews found on the island, a staggering six are considered to be endemic. Lilliputian they may be in size, but for any species, this is a more than commendable achievement.

Modest, and nocturnal, they rarely hit the headlines – yet this was what they did back on new year’s day 1924, a very special year for Joseph Pearson, a young biologist who had come to Sri Lanka from Liverpool to assume the position of Director of the Colombo Museum. That morning, as the rest of Colombo’s beau monde were nursing hangovers and trying to rid their heads of the tune of Auld Lang Syne, he discovered what would come to be called Pearson's Long-Clawed Shrew. At the time, it would have been a much more common sight than it is today, commonly found in forests and grasslands – habitats that are now so embattled as to render the endemic creature highly endangered. It is at the petite spectrum of island shrews, measuring just twelve centimetres nose to tail and sporting rather mundane grey brown fur.

The headlines screamed once more in 2007 when an entirely new endemic species of Sri Lankan shrew was agreed upon: the Sinharaja White-Toothed Shrew. The result of extensive research carried out by a handful of remarkable scientists, it was discovered that what had been masquerading in Sinharaja as the Ceylon Long-tailed Shrew was actually a quite different shrew species, and one that had, till then, not been properly recognised or identified. A closer study of its bone structure, taken with the simple observation that it had a shorter tail, resulted in the formal recognition of this new endemic species. However, the resulting Sinharaja White-Toothed Shrew is so restricted in distribution as to be almost entirely invisible – and has been found in only two areas of the edge of the Sinharaja Forest.

The island’s four other endemic shrews also amount to a shrew-spotters holy grail, being both highly endangered and markedly restricted to just certain parts of the island. At barely twenty centimetres long, nose to nail, with grey fur and a preference for subtropical or tropical forests, the Ceylon Jungle Shrew is determinedly nocturnal. At little more than centimetres nose to tail, the Ceylon Long-Tailed Shrew is so deeply threatened by habitat loss and logging that it has recently only been recorded in 5 highly fragmented areas in the Central and Sabaragamuwa provinces, despite its record of living as happily in the high mountain forests as much as the lowland ones. Covered in predictably modest brown fur with hints of grey, there is little about its appearance to help mark out the treasured and rare life it still attempts to cleave to, so validating that old adage: never judge a book (or shrew) by its cover. Barely any larger is the Ceylon Highland Shrew. Highly endangered and restricted to the central highlands of the country, it presents itself with an unapologetic style, being rat-like and grey, its take-it or-leave-it attitude of little help to environmental publicists eager to drum up the sympathy that any endangered animal merits.

The Ceylon Pigmy Shrew (Suncus Etruscus Fellowes-Gordoni) takes its characterization to heart, being so tiny as to barely measure nine centimetres, nose to tail. But though minuscule, it is a much more handsome shrew than many of its relatives and sports fur that is nicely chocolate brown to dark grey. As benefits so small a beast, it has a commendably long Latin moniker, much of it deriving from being named for Marjory née Fellowes-Gordon, the wife of the amateur Dutch naturalist who first recorded it. Highly endangered, it has been recorded as living in the low mountain rainforests of the Sabaragamuwa and Central Provinces, with a possible third sighting in the Western Province.

1856 was a big year for both shrews and people. The Crimea War came to an end, the Second Opium War erupted, the first casino was approved in Monte Carlo - and a diminutive nine inch shrew, to be named Horsfield’s Shrew, was discovered. But in the almost 200 years that were to follow, scientists gave what amounted to the cold shoulder to the pocket-sized beast; and even to this day it remains little understood or studied, its distribution across India and Sri Lanka only patchily comprehended, and its habits and description limited to a few notes about its unremarkable brown grey fur.

Obscurity has not troubled the Asian House Shrew - more notably called the Common Indian Musk Shrew - and it’s very close cousin, the Indian Grey Musk Rat Shrew. Both are so widely found as to be considered invasive species across South and Southeast Asia. Able to live almost anywhere, they breed with alarming ease and eat anything vaguely edible to keep their large rat like (fifteen centimetre nose to tail) bodies in peak condition.

But for Kelaart's Long Tailed Shrew a veil descends. A Burger from a long established family, and with numerous scientific discoveries to his name, Kelaart was also to be remembered as the man who discovered this species. Kelaart's Long tailed Shrew is now restricted to the grasslands, swamps and forest of Sri Lanka and southern India. A colossal (for shrews) twenty centimetres in length nose to tail, it has grey black fur and is ever more endangered, largely due to shrinking habitat options. The species has managed to cling to both its name and its original scientific evaluation, unlike many other shrews who suffer the continual revaluation, name changes and shifting designations of over busy shrew scientists; but not so poor Kelaart, who was to die, just forty one years old on a ship bound for England.


Squirrels

Remarkable for their extraordinary agility, speed, and balance, are Sri Lanka’s six squirrels. Not only can they leap up to 6 feet between branches, their 180 degree rotating ankles allow them to also climb or hang upside down with their heads facing forward. Their claws given them the surest of grips whilst their tails act as airborne rubbers for better steerage. Super-fast, their movements are crafted as much by careful forward planning as by learning. All feast off almost any plants including nuts, seeds, fruits, fungi, and green vegetation, and have been known to enrich their diet with bird eggs and insects too. Their constant nibbling of course wears down their teeth, and so, in a little bit of evolution that mankind might have benefited from as well, their teeth just keep on growing, to make up the loss. Collectively, they are what rats might be- if rats had any sense of fashion or PR. Nimble, beautiful, curious, and cute, they are rodents merely by genus. Even so, there remains something edgy about them. It is a squirrel after all who provokes the discovery of a massive diamond in F Scott Fitzgerald’s story “A Diamond as Big as the Ritz,” a tale of excess and debauchery.

The unrivalled leader of the squirrel world is the Grizzled Giant Squirrel, a massive beast, with a nose to tail length of 1.5 metres and death-defying skills enabling it to make the most impossible leaps from tree to tree. In Sri Lanka it hugs the central highlands and comes in 3 sub variants. The Highland Giant Squirrel which sometimes goes under the nom de plume of the Long-tailed Giant Squirrel has a pale tummy and a black head and upper body. It prefers life in hilly centre of the island – Kandy and Nuwara Eliya, for example. Smaller and lighter in colour is the Lowland Giant Squirrel sometimes rather unkindly called the Common Giant Squirrel. The last of the pack is the Grizzled Giant Squirrel - the king of the pack, with a nose to tail length of 1.5 metres and death-defying skills enabling it to make the most impossible leaps from tree to tree, hugging the central highlands.

All three are impressively indolent. Although they pretend to be active by day and sleep at night, their daytime activities usually cease after 10 am and only start again for a few hours after 4pm. In between these rare moments of activities they lie spread eagled across tree boughs or in specially built nests and wisely keep out of sight of villagers to whom their flesh is considered something of a delicacy. Grizzled brown, with white legs, stomach, and frosted face, they have excellent vision but poor hearing – which is something of a blessing for them as their cry - a shrill staccato cackle – is the sort of sound that can easily curdle milk.

But it is the Indian Giant Flying Squirrel that is the most mobile of all squirrels, elegantly avian due to the remarkable wing membrane it has evolved between its limbs to enable it to glide, parachute-style in total silence like the 1891 Lilienthal Glider that marked man’s first recoded flight, near Potsdam. When not in use this membrane is something of an encumbrance, restricting and slowing down its non-flight speed and agility and requiring a bizarre choreography of gliding and climbing to get back into its tree hole home. It comes in two sizes, the Grey Flying Squirrel being the largest opf the pair, silver grey to dark brown in colour with large eyes and is found throughout the central parts of the island. Lesser studied, shyer, and so endangered it is often considered extinct is the second flying squirrel, Small Flying Squirrel which sticks to the wet forested part of the island like the Knuckles Forest Reserve, Adam's Peak, Sinharaja and Kitulgala.

Two of Sri Lanka’s six squirrel species are endemic, the Dusky-Striped Squirrel and Layard's Palm Squirrel. Way back in 1913, the year before the great war, the year Picasso first lit up the art world, the squirrel world was lit by its own bright spotlight: an agreement between biologists – caried out through the good offices of the Journal of the Bombay Natural History Society, to redefine what was thought to be the Indian Nilgiri striped squirrel, as a quite separate species unique to Sri Lanka - the Dusky Striped Squirrel. To the casual observer the differences would be hard to spot but for punchi lena, as it is known in Sinhala, it meant recognition at long last. Despite being the smallest of the island’s squirrels, it is, at 60-70 grams, larger than its Nilgiri cousin, and spots longer, thicker stripes. But it is rare, keeping to the wet zone rainforests of the southwest like Sinharaja, though the odd sighting has also been made on Horton Plains, and in Nuwara Eliya, and Kandy.

The island’s only other endemic squirrel is Layard's Palm Squirrel - named for Edgar Leopold Layard, one of those legendary Victorian all-rounders, who took on a diplomatic career, the better to document the natural world, a passion he put down to lacking any siblings when growing up. He spent ten years on the island, leaving behind a variety of animals named after him, including a parrot and the squirrel that still bears his name. It is sometimes known as the Flame Striped Jungle Squirrel for the beautiful markings that run along its back. It is about thirty centimetres nose to tail, with black fur that fades to reddish brown on its stomach and can be seen all around the central highlands. By day they forage for fruit and nuts; by night they chatter from tree to tree, living, like swans, in pairs that bond for life. With their natural forest habitat eroded steadily, they are categorised as Vulnerable.

The final two squirrels on the island are ones shared with India. The Indian Palm or Three-Striped Palm Squirrel is the most common and widespread squirrel here, found in both rural and urban areas. Its markings are veery similar to those of the endemic Layard's Palm Squirrel, with whom it is often confused. The tiny dark brown Nilgiri Striped Squirrel is the mystery of the pack for almost nothing is known about it expect for the fact that it is different to the Dusky-Striped Squirrel, with which it was once confused. Indeed, some zoologists believe that it no longer exists on the island at all.

Gerbils

The last of the island rodents lives in a special category all of his own, the sole ambassador for a beast that boasts 110 spcies worldwide but just one in Sri Lanka. The Ceylon Gerbil or Antilope-Rat is the Cicero of the country, inquisitive, curious, social, and surprisingly uncuddely given their popularity as a pet, they have all the characteristics of that great plebeian, Cicero who rose to the highest offices of the Roman Republic before being murdered. Happily widespread, the Ceylon Gerbil (Tatera Indica Ceylonica) is a distinct variant of the Indian Gerbil. Well distributed across the island, it lives in small colonies inside nests lined with dry grasses at the end of deep labyrinthine burrows. It is notably unneighbourly, aggressive and territorial with gerbils from other colonies. Like most gerbils it is exhaustively fertile, with pregnancies lasting under a month that produce up to nine young - who will themselves reach sexual maturity within four months. It is tiny – little more than 4 centimetres head to tail and clothed in brownish grey fur, all the better to pass unnoticed. “Every animal,” noted Cicero in De Amicitia, his treatise on Friendship, “loves itself.” And were he here with us today, surviving the obscurity, poor press and endangered status of the island’s rodents and their closer cousins, he might have added, “and we must love them more.”