First paper from postdoc

I am really happy to announce that the first paper from my postdoc was just published online as early view.

It deals with a conceptual framework for dealing with detection issues when using camera traps to study animals. See: https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.4878

Here is the graphical abstract showing the six orders of detection

The processes that determine the probability of identifiably detecting an animal species divided into six spatial scales. Four scales for the probability that an animal passes a CT:1st order or distribution range scale, 2nd order or landscape scale, 3rd order or habitat patch scale, 4th order or microsite scale. The 5th order or CT scale for the probability that the animal triggers the PIR sensor of the camera and the 6th order or image scale for the probability that the animal is identifiably detected.

First day of field work in northern Sweden

I just had my first day in the field for my new job as a postdoctoral research fellow at the Swedish University of Agricultural Sciences. Although my work will mainly consist of analysing consisting datasets, I am also collecting new data. Most of the work is done my research assistants, but sometimes I get the opportunity to join them in the field!

A grid of sticks allows us to estimate effective detection distance and angle as well as animal speed.

February – Dissecting road kill

This weasel was caught by a cat, after which it was brought in for research.
This weasel was caught by a cat, after which it was brought in for research.

Dissecting road kill

I have been dissecting Mustelid traffic victims since 2006. It all started when I wanted to do voluntary work as a student for the Dutch Pine marten working group. I just moved to Wageningen and heard that there were possibilities to help with research on road kill. Soon I assisted Hugh Jansman and Sim Broekhuizen with their sections on pine martens. When I heard there were possibilities to help Jasja Dekker with sections on polecats, I started helping him as well, and by 2013 I took over the organisation of these sections. We study pine martens, stone martens, polecats, weasels and sometimes badgers, stoats and American mink. This month I organized the sections for the last time, as I don’t have that much spare time any more as I am in the last year of my PhD.

A young pine marten female which was found as a road kill near Deventer
A young pine marten female which was found as a road kill near Deventer

The traffic victims we study are mostly brought in by volunteers who find them on the road. We always start with measuring the total length of the animal, and it’s weight. After that we use the wear of the teeth as a measure of ageing the animals and we check for clear signs of trauma on the outside. Recently, another external feature was added, and nowadays, I also check the animals for ectoparasites, about which I wrote a short post last year.

A male polecat which was parasitized heavily by Ixodes hexagonus ticks.
A male polecat which was parasitized heavily by Ixodes hexagonus ticks.

After checking the animals from the outside, we cut them open to check and measure all kinds of things. We check for fat underneath the skin and around the kidneys, and weigh the fat stored in the mesentery to get an idea of the condition of the animal. We check for signs of reproduction, and we check for anomalies that could indicate the cause of death in case the animal was not found on a road. Doing this has taught me a lot about the biology of Mustelids, and it is a great way to get a close up look at these wonderful animals.

The author of a book on stone martens (Sim Broekhuizen) dissecting one of his favourite study animals.
The author of a book on stone martens (Sim Broekhuizen) dissecting one of his favourite study animals (a stone marten).

January – Counting Hibernating Bats

Baardvleermuis-op-het-plafond
A whiskered bat (Myotis mystacinus) hanging on the ceiling of the ruin of an old building

Counting hibernating bats

This year I will try to write a small story about one of my research related activities every month, and this month I will give a small account of the annual hibernating bat census. Every year many volunteers of the Dutch Mammal Society count bats in different places in the Netherlands. If I have time, I try to help Jasja Dekker with counting the bats around Wageningen. There are several different places we visit around Wageningen, namely, two old stone factories, an old ice cellar and several ruins of buildings.

Bats hibernate in winter, most probably due to the low abundance of insects in winter, on which they feed. Some species hibernate all through winter, but some species become active during warmer periods to feed on winter active insects such as winter moths. During hibernation, the bats lower their heart rate and breathing in order to lower their body temperature and metabolism. In this way they can spend days hanging from their feet. Depending on the species they will hibernate in more enclosed or more open spaces varying in moisture level and temperature. Therefore, a good hibernation site for bats has a variety in hiding places at different temperatures and moisture levels, to facilitate a multitude of species.

Today we started at the old stone factory near Rhenen in an area called ‘De Blauwe Kamer’. This stone factory was build around 1900 to fabricate bricks, but was discontinued in 1975. After that, some of the ruins were left, among which part of the big ring furnace. It is in this ring furnace that we count the bats. Although the space is quite large, it is difficult to look into all the cracks and crevices to find the hibernating bats. The ring furnace has openings to the outside, which means that there is a gradient in temperature and moisture level.

Jasja-breekt-zn-rug
Jasja is looking for bats in the old ring furnace of the stone factory ‘De Blauwe Kamer’

We found several species of bat, namely the brown long-eared bat (Plecotus auritus), Daubenton’s bat (Myotis daubentonii), Natterer’s bat (Myotis nattereri) and whiskered bat (Myotis mystacinus). It can be quiet difficult to find the bats in the first place, as you have to look above your head in the dark while trying not to stumble over the rubble that has accumulated over the decades after the factory stopped working.

Thijs-en-Marjolein
Thijs and Marjolein are working on the identification of a bat we found in between the bricks

Next to the stone factory ‘de Blauwe Kamer’, we visited several other sites among which the most notable are the old ice cellar at ‘Oranje Nassau Oord’ between Wageningen and Renkum and the old stone factory near Renkum. The old ice cellar is a fantastic site to look for bats, as the bats are hanging freely on the walls, which makes identification and finding them a lot easier, but which also makes this object more prone to disturbance, as the bats can’t hide away in between the bricks. Unfortunately, my flashes were not working properly at the moment we visited the cellar, so I don’t have any pictures from this site this year. After the cellar we went to several ruins of old buildings at a place called Buunderkamp. Depending on the weather you can find more or less bats here, as the sites are very exposed. Luckily, today was not that cold, so there were still some bats hanging from the ceilings, such as the whiskered bat at the top of this post.

The old stone factory near Renkum is a similar object to the old stone factory ‘De Blauwe Kamer’, but the type of furnaces were different, which results in a lot of small tunnels instead of one large one. These small tunnels are not very suitable for photography, so no pictures from here either.

Franjestaart-tussen-de-stenen
Hibernating Natterer’s bat (Myotis nattereri) in between the bricks in the old ring furnace of stone factory ‘De Blauwe Kamer’.

Photo of the Month

Unfortunately, recently there has been a problem with the server which hosts this site, which has resulted in part of my posts disappearing in internet space. All my updates since June 2014 have disappeared, including all the photos of the month since that time until now (December 2014).

I have decided to stop my photo of the month posts as of January 2015, so this will be the last post as photo of the month. I will try to post regular updates on my photography or research.

Photo of the Month July 2014

2014-07

Photo of the Month August 2014 2014-08

Photo of the Month September 2014 2014-09

Photo of the Month October 2014 2014-10

Photo of the Month November 2014 2014-11

Photo of the Month December 2014 2014-12

Photo of the Month June 2014

Photo of the Month June 2014Evening Chamois

In the beginning of last month, I spend a week in the Hautes Vosges in France together with my father (Ronald Hofmeester). We spend some time photographing landscapes and flowers, but the most impressing memories are of the moments spend photographing chamois. In comparison to other areas where I have seen chamois, the chamois in the Hautes Vosges are relatively easy to see up close. With a little bit of patience, perseverance and luck you can get pretty close to the animals and photograph them showing natural behaviour. We have photographed them in the mist, in early morning light and in evening light (see also my portfolio page: Light and Dark – Hautes Vosges), but the most intense was the last evening of our trip, when we had about 30 chamois all foraging in the evening light. This picture was taken on that last evening, of a relatively young chamois looking up the hill into the sunset.

Canon 5D mIII, 420mm, 1/1000 @ f/7.1, iso 800

Photo of the Month May 2014

Photo of the Month May 2014Fresh leaves

Spring was early this year, and halfway April, the leaves were appearing on the beech trees again. As I wrote in my text for the Photo of the Month March I wanted to spend part of my photographic time this year on the many shapes and forms made by trees. So when I saw the fresh spring leaves appearing, I immediately set out to get a photograph depicting the feeling I got from these fresh leaves. Finding the right setting took some time, but I found what I was looking for in these three leaves. What really amazed me, was that the many insects feeding on the leaves had also appeared already, as shown by the many holes in the leaves. Amazing, what a little rise in temperature and lengthening of the days does to the natural world!

Canon 5D mIII, Canon 100mm macro, 1/100 @ f/3.2, iso 400

Radio exposure

Foto Vara's Vroege VogelsThis morning I was on Dutch radio with a small interview concerning my research on ticks on medium-sized mammals in the Netherlands with the use of traffic victims. It is in Dutch, and can be found on the Vroege Vogels Website.

If you find a traffic victim of a hare, pine marten or polecat, in a forested area please contact me, as it could be interesting for my research!