Spot the Nilgiri Marten!

September 21, 2015 • 1:57 pm

by Matthew Cobb

Aditya Gangadharan (aka @AdityaGangadh) posted this pic on Twitter. To give you a hint, a Marten is a mustelid (methinks it is like a weasel), about 50 cm long, with a tail that is slightly shorter. So we ain’t talking nightjars! Click twice to embiggen sans book adverts, comme d’hab’.

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Wikipedia claims:

Very little is known about the Nilgiri marten. It is diurnal, and though arboreal, descends to the ground occasionally. It is reported to prey on birds, small mammals and insects such as cicadas.

I was partly attracted to this photo because the Nilgiri Marten is found in the Nilgiri hills in south-western India. For several years, together with ant-expert Christian Peeters, I worked on a population of ant from this region, called Diacamma. Diacamma ants are queenless – they have lost the queen caste, and one worker dominates the others. She is called a gamergate (pronounced gammergate – the word means, or perhaps meant, given that there’s now another meaning, ‘married worker’) and lacks the large ovaries and wings typical of queens.

This situation is typical of many Ponerine ants, but what is weird about Diacamma is that they possess external glands called gemmae – apparently based on wings – that enable them to produce pheromones and to mate. The dominant female hangs around the cocoons waiting for the new ants to hatch out, and she then bites off their gemmae, effectively sterilising her sisters (and later, her daughters). (We studied how this takes place – contact me if you want a copy of the article, as the full article is behind a paywall.)

When the gamergate dies, or the colony splits and half the colony no longer has a gamergate, the first female to hatch out is not mutilated (there’s no one there to do it), so she becomes the new dominant. For pictures of the gemmae go here.

This situation exists in all Diacamma ants, except the Nilgiri population, where no mutilation takes place and the gamergate imposes her dominance physically, as in other Ponerines. This group is not a separate species from the local D. ceylonense, as the two taxa will interbreed (we succeeded in doing this in the lab – a big deal if you work on ants). You can read an abstract from a recent paper by Christian Peeters here.

The scrappy ground seen in the photo is the kind of place you get Diacamma ants – there might even be some mooching around…

 

30 thoughts on “Spot the Nilgiri Marten!

    1. I take it the ants aren’t in the white bit.

      (Second reaction – if that’s near the ‘Nilgiri Hills in south-western India’ I’ll eat a Nilgiri Marten, raw)

      cr

        1. My impression (off the top of my head) is that the Nilgiris in the south are some thousands of feet high. A worthy range of hills, but not nearly high enough to have snow at that latitude. They were (as I recall) a ‘hill station’, where the sahibs went to get away from the heat. I think there’s still a narrow-gauge railway, now a tourist line, up them.

          (In fact a quick Google says the highest is 8650 feet, a worthy mountain, but I doubt it ever gets snow in the tropics).

          cr

    1. I saw a couple of other possibilities, but not that one. However, mine weren’t black, so given its name, I’m going with you.

    2. Thanks for pointing this out. I was distracted by the squirrel-like animal, also at the right side, but about 25% up from the bottom prostrate behind the stick-stumpy thing. It’s facing right and is grey with what seems to be a bushy tail at the left end. An eye and a pinkish ear are visible but at the other end,of course.

    3. yup, you’re correct. I did not see that. and now, I’m wondering if I was just putting shadows together and my brain went into ‘squirrel recognition’ mode. I still see the ‘face’, but it’s not as clear. JEBUS was a SQUIRREL!!!!@

  1. I won’t give it away entirely, but the face and eye are clearly visible. The animal is facing toward the left of the picture.

    Question about the ants. I did not know that queenless ants existed. Which leads me to a reflect that I don’t know how or when a queen caste evolved in hymenoptera. Is this a trait that occurred in the common ancestor of these insects or is there something about hymnenoptera (perhaps sex determination?) that makes lineages likely to evolve a royal caste. If we assume the latter, then the primitive states of ant ancestors was queenless. Do these ants merely preserve the primitive state (I’d say the presences of some kind of derived wing in this genus could be evidence for retained primitivity, but I suppose genetic evidence would be best) or did they ‘lose’ queens along the way? And is the case for other queenless ants the same or different?

    All of this may be well known, so feel free to merely point me in the direction of a publication if such exists.

    1. Great questions! These ants are “derived”, that is, they have lost the queen caste. It’s not clear why, but it must be linked with ecology. No queen means a small colony (a reproductive worker has much smaller ovaries, so fewer eggs), and lack of winged females (males are still winged) means that colony dispersal takes place when a colony divides and some of the workers and the gamergate move off, which can’t be very far. (I don’t think this has ever been observed in nature). However, the social organisation may be typical of the early stages of evolution before the appearance of queens.

      1. Dear Dr Cobb,
        I should be very interested in a copy of your paper on the ants. All hymenoptera fascinate me (as do orthoptera).

    2. Nope, it is facing right. I think you might be looking at the rocks near the centre of the picture. That was my first guess as well.

    1. Have a look at the picture Taz posted above, then go back and look at where jblilie instructed us to. (That’s how I did it…)

  2. Given the context:

    “She is called a gamergate (pronounced gammergate – the word means, or perhaps meant, given that there’s now another meaning, ‘married worker’)…”

    …it sounds to me like Matthew’s gamergate certainly precedes the recent brouhaha (to which he refers as “now another meaning”). And it’s pronounced differently!

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