21 April 2018

Paarl Data - The Predators

In recent years the Paarl Mountain Nature Reserve has been home to more than 11 wild mammalian predators. By far the most common species are the Large-Spotted Genet and Small Grey Mongoose, but there is also an alarming number of domestic dogs and cats that roam the reserve.

In this blog post I want to focus on the similarities and differences between the Large-Spotted Genet and Small Grey Mongoose at the reserve.

Small Grey Mongoose (Kleingrysmuishond - Herpestes pulverulentus) wearing its favorite black boots

These species are more or less the same size and both prey on small mammals. Both species were camera trapped throughout most of the reserve, with a strong focus on areas where I setup the camera traps to target rodents.

However, one big differences between these species is when they are active.

Although they occur in basically the same areas and hunt the same type of prey, there is practically no overlap in terms of when they are active. As a result there is less direct competition between these species, compared to if they were active at the same time.

Large-Spotted Genet (Grootkolmuskeljaatkat - Genetta tigrina) on its nightly patrol

One of the most peculiar aspects of the difference between these predators, and the reason for this post, is the moon. As one might expect the Small Grey Mongoose doesn't really care about the phase of the moon, yet the Large-Spotted Genet is keenly aware of it.

The Large-Spotted Genet has a clear preference for nights with low moonlight. The data even shows a tendency towards being more active when the moon isn't yet out.

I'm not sure why the Genet is biased towards darker nights. Maybe such nights give a hunting advantage to the Genet, making it harder for its prey to see it? Or maybe the opposite is true, that the Genet finds it harder to see the rodents on darker nights and thus needs to search for them more actively?

I decided to pull the combined "Rodent" data to compare the results with those of the Genet.

This charts shows a combination of all small rodent-like animals

Very interesting! From this we see that the Rodents have the opposite bias as the Genet.

I included the baseline data to make sure that I'm not just dealing with sampling errors (maybe only sampling during full moon periods, which is clearly not the case here).

I'm still not sure what the nature of this interaction is, but it definitely seems to be something to keep an eye on. For now the mystery remains...

Cape Clawless Otter (Groototter - Aonyx capensis) near a stream on Paarl Mountain

Below is a list of all the predator species I managed to camera trap during August 2016 to November 2017. I'm happy with the results, but there are some species that have managed to dodge the camera traps.

In particular I missed both the Cape Fox and Honey Badger, but both have been captured on the reserve's own camera traps in the past, so they are definitely around.