31 May 2018

In A Drop Of Water

I recently had a little money set aside to buy something fun for myself. I've always wanted to play around with a microscope, so I searched online for a decent (but cheap) microscope. I'm pretty happy with my purchase, but I don't get around to using it as often as I would like.

Below are a few images and video clips of the tiny critters I have found in water (fresh and sea) near our family holiday home in the Eastern Cape.

First up is an insect larva.

Insect larva as seen under a microscope

I initially thought that this might be a fly larva, but after posting the observation to iNaturalist I learnt that a number of different kinds of insect can have microscopic larva.

Video: Tiny insect lava found in fresh water

The water samples are often full of single cellular creatures.

A large single-cellular Diatome found in a drop of lagoon water

I'm not sure about the really small ones, but I believe these bigger ones are called Diatomes.

Video: A large Diatome swimming slowly under the microscope

One of the coolest creatures to find is the Rotifer. This little guy was found in our large bird bath.

A Rotifer can zip along using jet propulsion, although they also like to "walk"

Rotifers have the ability to create a strong water current around them that sweeps food into their mouths. They even have a tiny brain which, according to Wikipedia, operates about 250 of the 1000 cells that make up a Rotifer!

Video: Rotifer creates a strong current of water near it

I found this worm-like creature in a water sample I took from the rocky beach.

Maybe a Nematode?

I'm still not sure what exactly it is, but I think it is a Nematode.

Video: Worm-like-thing squirming underneath the microscope

Last, but not least, is this amazing little creature.

Maybe a type of Protozoan organism?

Again I have no idea what this might be. It was very small, so I want to guess it is a Protozoan, but it seems to be a fairly complex life form, so I'm not sure...

Video: I think it is feeding on the stuff to the left of the screen

I keen observer might have noticed that the photo and video quality isn't very good... Well that would be because I'm trying to hold my mobile phone at exactly the right spot to project the image from the eyepiece onto the phone's camera censor... But it is better than nothing and I'm happy to have a way of sharing this strange world with you folks out there.

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.

31 March 2018

My First Tiger-Bush-Cat

Serval (Tierboskat - Leptailurus serval) in the Drakensberg

I'm just back from a wonderful trip to the Drakensberg. The scenery was amazing, but the highlight of the trip was seeing my first Serval.

Showing off those white spots behind the ears

Servals like to live near water sources with adjacent high grassland, reed beds or other dense vegetation such as forest edges, etc. They have a fondness for Vlei Rats, but also pray on other small mammals, birds and reptiles. They will even eat insects. Servals are mainly active at night, but are also sometimes seen during dawn/dust and on cooler days. This sighting was on a cool overcast and rainy day.

Drakensberg scenery on a more sunny day

I recently took the plunge into citizen science (after a bit of a jaded past) and I must say I've been enjoying it greatly (well for the most part at least). The platform provided by iNaturalist is really amazing.

Since I got back I've been busy importing the photos into WildLog and then uploading the observations to iNaturalist.

You can go to the iNaturalist site to see all my observations from the trip.

24 February 2018

Paarl Data - Two Antelope And A Bird

I've been fortunate to get a good number of camera trap observations for both Duiker and Grysbok at Paarl Mountain Nature Reserve. It provides a great opportunity to compare these two antelope species.

The Common Duiker (Duiker - Sylvicapra grimmia) at Paarl are eager to help

Lets start by comparing the occurrence pattern for both species on the reserve. It is much easier to compare Duiker and Grysbok than it is to compare something like Duiker and Small Gray Mongoose, because if the camera trap is setup to capture photos of a Duiker then it will also capture a Grysbok, but not necessarily a mongoose.


From the abundance maps it is clear that the two species overlap throughout most of the reserve. But there are some small differences: The Duiker is a bit more strongly associated with the fire breaks and the Grysbok seem to penetrate the think vegetation more easily. The big difference is the patch at the south-east of the reserve. This area burnt a few years ago and the vegetation in the area is still fairly short. I suspect that the Grysbok is quicker to recolonize such areas. It will be interesting to see whether the same area contain Duiker a few years from now when the vegetation is more dense and mature.

The problem with the using the occurrence map, above as a "distribution map" is that not all areas of the reserve was sampled to the same degree. For example the far south was not sampled at all. To confirm that there is a relationship between Duiker and Grysbok observations I decided to evaluate the data as well.

A Cape Francolin (Kaapse Fisant - Pternistis capensis) a bit unsure about this whole analysis business

I compared the number of times Duiker, Grysbok and Cape Francolin were observed within two days of each other and in the same general area. I included Cape Francolin because it is another very common species and will be captured by camera traps that are setup to targeting the antelope species.


As expected the Duiker and Grysbok show a strong relationship, but surprisingly there is a big difference between how the Cape Francolin relates to the two antelope species. I decided to pull up the abundance map for the Cape Francolin, suspecting that it might illuminate why there is such a discrepancy.


The map explains suggests that both the Grysbok and Cape Francolin are present in the recently burnt area where the Duiker is still absent. The Cape Francolin also shows the trend of being less strongly linked to the fire breaks and readily penetrating the thinly vegetated areas.

Cape Grysbok (Kaapse Grysbok - Raphicerus melanotis) helping capture data during the night shift

The males of both Duiker and Grysbok are the only ones to have horns, making it possible to determine the gender. Both species show the same common trend: The males are either more active or more common when compared to the females. My feeling is that they are more active and not necessarily more common.



I also like to compare the day-night activity patterns of the species. Again both species show more or less the same pattern.


I don't use the actual time, but instead like to use a time of day category. The reason for this is because the length of the day changes a lot between winter and summer. So I devised a way of splitting the day and night into categories based on the time when sunrise and sunset occurs. Doing so shows a subtle difference between these two species: Although the trend remains more or less the same, the Grysbok show an odd spike in activity during the late afternoon. It seems like they become active sooner before sunset and remain active longer after sunrise.


I also like to compare the possible influence the phase of the moon might have on the species. Both species show a very similar trend, but again there are minor differences: For some reason Duiker activity is surprisingly low on nights with a dark moon. The Grysbok pattern follows the expected baseline pattern very well with a slight increase towards the start of the full moon cycle.


The last comparison I want to make in this blog post is the chance of getting subsequent visits of the same species during one day-night cycle. Although the Grysbok is the more common species it is the Duiker that is more likely to have multiple observations in the same day-night cycle.


I really enjoy doing these analysis, and I hope to a couple more of these of the next month or two.

29 January 2018

Rock Rats

The Namaqua Rock Rat was one of the most frequently camera trapped rodents at Paarl Mountain Nature Reserve.

Namaqua Rock Rat (Namakwa-Klipmuis  - Micaelamys namaquensis) at Paarl Mountain

Based on my data, these rodents are mostly nocturnal. However, they show a very strong preference for the twilight hours, more so than any of the other rodent species camera trapped on the reserve. I might go as far as to say they have crepuscular tendencies...

Mother and youngster during early morning twilight

Interestingly two thirds of all observations were during times when the moon was more than 50% full. The exact opposite is true of the Large-Spotted Genet, which is a nocturnal predator and always on the lookout for rodents... I wonder, is this difference due to the genet having to work harder to find the rock rats during the dark nights, or are the rock rats more vulnerable to predation on dark nights and thus don't move around as much?

Showing off his bad ass notched ear

I also noticed more individuals with notched ears than I'm used to seeing in other rodent species. I'm not sure what the cause is, but I'm guessing it is related to living in between the rock crevices. Or maybe it is simply part of their hidden rock and roll lifestyle.