Let’s talk about rats … cute native Australian ones …

Fig. 1. Chicago from the John Hancock building (Photo: T. Rymer)

 

Moving on to Blog 7, we’ll be taking a different view from this month of July. We’re more than half way through the year right now, and I’m writing this from the gangster-ridden, speak-easy city of Chicago! (Figure 1). I thought I would take a bit of time to talk about some of the work we’ve been doing on native Australian fawn-footed mosaic-tailed rats Melomys cervinipes (Figure 2). There will hopefully be lots more of this to come in the future.

For starters, I thought I’d take a bit of time to introduce you to this little rat. I coordinated a group of postgraduate and honours students to collate data from a variety of studies into a single work representing the biology, ecology and life history of this species, which we published as a species account in the journal Mammalian Species. We presented a taxonomic account at the species level, providing a species diagnosis and general characters description. We also provided notes on the distribution and fossil record accounts. Finally, we collated information on the form and function, ontogeny and reproduction, ecology, behaviour, genetics and conservation of the species.

Fig. 2. Female fawn-footed mosaic-tailed rat (Photo: T. Rymer)

The species belongs to order Rodentia, family Muridae, sub-family Murinae, tribe Uryomyini. The species was first described by Gould in 1852, and placed in the genus Mus. The specimen was a female, and it is the designated lectotype. The type locality was named as Stradbrook Island (Figure 3) in Moreton Bay, Queensland, Australia. The first occurrence of the current name combination is recorded by Thomas in 1922. The genus Melomys comprises 21 species, of which three are native to Australia. A 4^th species, Melomys rubicola was declared extinct in 2014. No subspecies are recognised within M. cervinipes. The generic name, Melomys is derived from the English Melanesia, indicating the wide distribution of species from this genus, and the Greek mys for mouse. The species name cervinipes is from the Latin cerv for deer or fawn and pes for foot, referring to the light colouring (fawn) of the feet.

Fig. 3. Stradbroke Island, Australia

Melomys cervinipes is small, light grey-brown to russet brown (Figure 2), although colour is highly variable and can change with age, with a white to cream ventral surface, a brown to black tail, and light fawn-coloured feet. Young animals are often a uniform light grey. The fur is soft, fine, and long, and dark whiskers are conspicuous on the muzzle. The ears are short, rounded, and dark grey to black, and the eyes bulge conspicuously. The tail is naked, with the scales arranged in a mosaic-like pattern, interlocking with little overlap, with short hairs, and is approximately equal to the head–body length. The tail is partially prehensile, with the tip capable of curving round objects to potentially provide support. The hind feet are long and wide. Average body mass is 72.9 ± 12 g, average head–body length is 133.5 ± 12.7 mm, average tail length is 142.6 ± 10.9 mm, average hind foot length is 27.5 ± 0.8 mm and average ear length is 18.3 ± 1.6 mm.

Distinguishing this species from its sister taxon Melomys burtoni in the field is challenging. However, some techniques have been used, including counting the number of tail scale rows (13 vs. 14-15), and length of 1^st and 5^th inter-digital pads (1^st = > 2.3mm; 5^th = > 1.7mm indicating M. cervinipes). Dentition provides a more accurate estimate, but is not possible for living wild animals.

In the next blog, I’ll continue to describe the basic biology of this fascinating little rat.

 

You can read more about my research in my publications, listed on my blog. You can also find me on ResearchGate, the James Cook University website and Twitter.