Thursday, 9 May 2013

What Happened to Hong Kong’s Sladen’s Rat

The second non-urban or hillside rat in Hong Kong was called Sladen’s Rat in the 1960s with the scientific name of Rattus rattus sladeni. However, it was evident even then that there was something very wrong with the taxonomy and/or identity of the rats in Hong Kong. One of the urban rats is the Black or Roof Rat (Rattus rattus), then assigned to the subspecies flavipectus. This form was thought to be native to southern China but it could, of course, have been a population derived from the native form and others brought in by ship as Hong Kong developed into a massive port from the 1840s.

The presence of two sympatric sub-species occurring as two distinct populations was clearly nonsensical. They did not appear to interbreed and sometimes their habitats overlapped. Chung Ka Bun, in his work on the two hillside rats, noted that the Buff-breasted (Rattus rattus flavipectus) occasionally strayed into the main study area, i.e. the one occupied by the so-called Sladen’s.

I have not been able to find who identified the form that occurs in Kong Kong as Sladen’s Rat. The authority usually referred to were Allen (1938) and Ellerman (1941) but they do not refer to Hong Kong or that region of China.

More recently, for reasons that will become apparent below, I found Richard Corlett’s 2001 article in Porcupine entitled, The Naming of Rats. He began his article by writing:

Whoever said "Fools rush in where angels fear to tread" was surely thinking of rat taxonomy. I am therefore approaching this topic with some trepidation, but also, I hope, more as an unusually brave angel than a complete fool.

It seems that the Hong Kong rat we knew as Sladen’s Rat never was Sladen’s Rat or what became of it in the taxonomic reshuffles. From the British Museum, Corbet & Hill (1992) said it was Rattus remotus while Musser at the American Museum of Natural History called it Rattus sikkimensis. Corlett wrote that these names seemed to be complete synonyms, referring to the same species that occurs from Nepal to South China, and south to Thailand. Sikkim Rat was used as the common name on the Smithsonian Institution website but in Hong Kong there was no common name.

Rattus sikkimensis seems to have been adopted as the scientific name by those working in the University of Hong Kong. However, there is a further twist in the story. While remotus  (named by Robinson & Kloss in 1914) has priority over sikkimensis (Hinton, 1919), both names fall since they are both now included in Rattus andamanensis (Blyth, 1860) which has priority. Full details of the current nomenclature together with a bibliography (including Hong Kong) are given in the IUCN website. There, the common name is shown as Indochinese Forest Rat or Sikkim Rat. The former seems appropriate for Hong Kong usage.

The reason I looked up ‘Sladen’s Rat’ was because I was telling somebody about a very bright individual of this species and wondered if anything had been done to sort out the anomalous taxonomy. The University of Hong Kong in the 1960s would not pay for air conditioning for people but it would pay for air conditioning for equipment or animals. Therefore, if one could contrive laboratory/office space in an equipment or animal room, it was actually possible to get some work done during summer afternoons when the outdoor temperature would be in excess of 90°F (36°C) and the relative humidity higher than 90%.

We set up shop in an old animal room vacated by the medical school and taken over by Zoology. We knew a few Sladen’s rats had escaped from one of the rooms while being moved. I had my desk (a grotty old table covered in brown paper) under a window; my wife had her desk under another. Having worked all morning on salt glands, we had our lunch at our desks in the same room. I leant back to stretch and noticed a small hole in the corner of the ceiling above me. The next day the whole was a little larger; the next day larger still. Then, one day, a rat’s nose appeared in the hole. After a week or so the hole was about 40 cm in diameter and by this time the rat could put its head through the hole. Each morning our friend appeared and there it slept during the day, inhaling cool air from the room while ignoring all the activity below. One cool rat.

Further Reading and Links

Marshall, P 1967 Wild Mammals of Hong Hong. Hong Kong: Oxford University Press.
Chung, Ka-bun 1971 An ecological study of two species of hillside rats in Hong Kong.
PhD Thesis, University of Hong Kong
Allen, GM 1938 The Mammals of China and Mongolia. Natural History of Central Asia Series, Vol. XI, American Museum of Natural History, New York
Ellerman, JR 1941 The Families and Genera of Living Rodents. Vol. II. British Museum (Natural History), London
Corlett, R 2001 The naming of rats. Porcupine No 23, July 2001
Corbet, GB & Hill, JE 1992 The Mammals of the Indomalayan Region: a Systematic Review. Oxford: Oxford University Press.
Chung, K 2003 Hong Kong’s common rat species. Porcupine No 29, August 2003
IUCN - Rattus andamanensis (with bibliography of taxonomy)