Sri Lanka, like ancient Rome, has strict - albeit invisible - notions of caste and class. And class, not being exclusively human, is no less apparent within its smaller mammalian world – its rodents, and rodent-like cousins: its rats, shrews, mice, and squirrels.

If the island’s tiny and elite mammalian senatorial class is represented by its elephants and leopards, its more capacious equestrian class comprises its monkeys, lorises, bears, mongooses, buffalo, anteaters, otters, jackals, hares, deer, civets, and wild cats.

Which, of course, leaves the plebs. Bottom of the pyramid, they may have been, but the Roman pleb took nothing lying down. Famed for their resistance, resilience, and passion, they lived their lives with little submission or demureness. They were eminent, not intimidated. As are Sri Lanka’s rodents, whose existence is anything but deferential or docile. And numbering over 30, they make up not just over a quarter of the island’s land-living mammal species, but also 50% of its endemic species. To know them is to understand a key part of what really makes Sri Lanka Sri Lankan.

Naturally, plebs had a firm pecking order all of their own and at its apex stood the Tribunes of the plebs – the People’s Tribune, which in a mammalian context can only mean the rats. Like tribunes, rats are the busy, brisk, no-nonsense influencers of what really happens or doesn’t, and they abound in Sri Lanka. Their collective poor reputation and cordial hosting of many especially nasty diseases mark them out as a mammal best enjoyed from a distance. However, as Jo Nesbo observed, "a rat is neither good nor evil. It does what a rat has to do."

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 scarcer, as biologists have counted. Its only other endemic cousin, the Nilgiri Rat, is no less endangered and is today found only in restricted highland locations such as the Knuckles, Horton Plains, and Nuwara Eliya. Little more than thirty-nine centimetres in 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 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 is 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 in length, nose to tail. It is found in significant numbers throughout India and Sri Lanka, and its fondness for burrowing in farmland and gardens has earned 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 occurs in at least five distinct subspecies: the Common House Rat, the Egyptian House Rat, the Indian House Rat, the Common Ceylon House Rat, and the Ceylon Highland Rat. None is much longer than thirty-three centimetres nose to tail, and despite their reputation for being black, they also sport the occasional lighter brown fur. They are phenomenally successful, with almost every country in the world calling them home, including Sri Lanka. They are also disconcertingly resilient transmitters of many diseases, with their blood serving as a habitat for large numbers of infectious bacteria, including those that cause the bubonic plague.

Three other rats are restricted to South Asia: Blanford's Rat, the Indian Bush Rat, and the Indian Soft-Furred Rat. Indeed, Blanford's Rat, also known as the 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 India and Sri Lanka. 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. It has rather beautiful fur that is speckled yellow, black, and reddish, as if it had wandered out of a hair salon, unable to make up its mind about which exact hair dye to 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 is listed 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 alternative names all associated either with Lucifer, Satan, Abaddon, Beelzebub, or streets, sewers, or wharves. Immortalised 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 nearly anything, is highly social, produces up to 5 litters a year, and, according to more informed scientists, is capable of experiencing positive emotions. A final rat, Tatera Sinhaleya, known only from fossil records, bade farewell to the island many thousands of years ago.

If rats are the tribunes of the mammalian world, then mice are certainly its aediles, a post in the Roman Republic reserved for men responsible for the upkeep of the city, and so, by nature, meticulous, attentive, persistent. Just like Sri Lanka’s seven mouse species, nearly half of which are also endemic.

The ultra-rare Sri Lankan Spiny Mouse leads these native, endemic, and patriotic rodents. It is now so endangered that it can be seen in only very few locations. A mere maximum of 18 centimetres in 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 similar, 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; both are covered with reddish-grey fur and exhibit relatively 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: from mites, ticks, and sucking lice to small scorpions.

The last of the endemic mice is the Ceylon Highland Long-Tailed Tree Mouse. Discovered in 1929 by t...