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’.
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…