Help with id of rodent in Nairobi National Park

heron with rodent in beak.jpg

I am sorry this is probably going to be a tough id. It is a rodent caught and eaten in front of my eyes by a young Black-headed Heron. The event ocurred within a dozen meters or so of the edge of Athi Dam in Nairobi National Park about 30 years ago (I am reviewing some old slides I have).

The general shape of the rodent reminds me of a picture I’ve seen of an African Marsh Rat Dasymys incomtus.

My fieldnotes say that the heron “was staring at the ground with legs half-bent, it speared its beak into the grass and brought up a brown-furred rodent with a bright red tail, rapidly paddling its feet. After a short while, the heron swallowed the rodent.”

Any insights as to the rodent’s identity?

Saludos,

Héctor

 

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6 Comments on “Help with id of rodent in Nairobi National Park”

  1. vdinets Says:

    I can’t think of anything with bright red tail. Could be a result of trauma.

    • hectorgom Says:

      Thank you. Let’s suppose it may have been fresh blood that had soaked its tail. From the general size and shape, do you have any ideas regarding the id?

  2. Charles Foley Says:

    Hi Hector,

    Very difficult to help narrow it down with the fairly limited information you were able to collect. I would say Arvicanthis, Otomys and Dasymys are you most likely options, given the size, but you’d need to know more about body size to tail length etc to narrow it down much further. Some Arvicanthis have reddish on the rump and around the face, but that doesn’t seem to be what you’re describing.

    Charles

    • hectorgom Says:

      Thanks very much for narrowing it down! Researching the 3 genera you mentioned, I ended up identifying the following species as potentially ocurring in NNP: Arvicanthis nairobae, Otomys angoniensis, (Otomys tropicalis and typus occur at higher elevations), and Dasymys incomtus. Then I studied other details and found that Arvicanthis nairobae is too small and has tail around 70% of body length (too long to match my rodent) but Dasymys incomtus is just right: about 50% larger than A. nairobae and its tail is about 50% of head and body length.

      • hectorgom Says:

        Sorry, I think that two lines of text got snipped out or something like that. What I meant was that thanks to Charles Foley’s narrowing down the list of possibilities, I was able to identify it as Otomys angoniensis, because Arvicanthis nairobae is too small and has a tail around 70% of body length and Dasymys incomtus has a tail 90% of body length; on the other hand, Otomys angoniensis is just right with a tail about 50% of head and body length.


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