EPOW Ecology Picture of the Week -- The Leopard That Is A Tortoise: Part II, Mystery

Explanation: Last week, we encountered this wonderful domed reptile of eastern Africa: the leopard tortoise. But upon close examination emerges a mystery of ecology and further encounters between species.

Look closely at the main photo, above.

Who are these flies and what are they doing, all lined up along one of the growth rings on the tortoise's back?

Like many other turtles, tortoises grow their shells by adding onto each scute or plate from below. This shows up as "growth rings." They usually can't be read as accurately as growth rings of trees can in temperate forest areas, but they do give a general indication of relative age.

How many growth rings can you count on this one scute? The count may not be an accurate way to age this tortoise but the number, along with the overall large size of the shell, suggests that this critter has been around for a long time, indeed.

All well and good ... but what are the flies that have clustered here onto one of the growth rings? One might hypothesize that they are using the tiny niche space to lay their eggs, although I saw no evidence of this, and nor do flies usually lay eggs in groups. Perhaps they have found moisture or salts that have nestled into this particular suture line.

To me, these flies look similar to tse-tse flies I had encountered in Malawi. But if that is their identification, I still cannot determine what they are doing. 'Tis an African Mystery!

Do leopard tortoises provide some kind of
micro-habitat for symbiotic fly species?
Far stranger things have been discovered in nature!

And there may be some benefit to humans
to unravel this minor mystery.

EPOW - Ecology Picture of the Week