A sad otter's tale

The purpose of this post is to raise awareness about otter road casualties and illegal or unintended trapping.

Last week (9th January) saw the tragic death of a beautiful Eurasian otter (Lutra lutra).

It was on my way to the Middle Level Commissioners (MLC) offices in March (Cambridgeshire) that I spotted the corpse on the side of a busy main road and I pulled over to take a look. Once I had reached the otter, I realised that it was probably a relatively young animal, since it wasn't much bigger than a domestic cat.

The hind feet of the otter corpse (09/01/2018).

With a pang of sadness (otters are one of my favourite animals), I saw that it had a head wound, most likely from a collision with a car. The pool of blood in which the otter lay was relatively fresh and very little smell issued from the body, indicating that it had not been there long, probably around 48 hours.

A closer inspection of the animal revealed that its abdomen was slightly swollen and that it had enlarged nipples. Whether these two observations were due to rigor mortis, or the animal being a pregnant or recently pregnant female, I do not know...  I hope it was not carrying pups.

The enlarged and exposed nipples of the otter - unknown to be a result of rigor mortis or pregnancy (09/01/2018).

WARNING: graphic content below

The dead otter which I found in the Cambridgeshire Fens on the 9th January 2018 (glove for scale).

To bring some positive light to the sad situation, I thought that I had better collect the otter in order for it to be sent away by the Environment Agency for post-mortem research by the Cardiff University Otter Project (CUOP). Making use of my car windscreen sun shield, I wrapped up the body and gently carried it to the boot of my car. It must be said that I was surprised at how heavy even a reasonably small otter weighed...

After a quick phone call with my line-manager (Cliff Carson, Environmental Officer at the MLC), he agreed for me to leave the corpse at his house so that we could take it to the Brampton Environment Agency Office the following morning.

Before transferring the body the following morning, we took a few measurements ('weight', 'nose to tail length' and 'nose to anus' length). See below for a comparison of the measurements with those of an average individual for the species. Note that the 'nose to anus length' and 'weight' are lower than that of the average measurements for the species, indicating that it was a relatively small, perhaps sub-adult/juvenile.

Comparison of otter measurements with those of a standard otter.

Once at the Brampton Environment Agency Office, we met with a lady called Sue who is responsible for sending dead otters from the local area to Cardiff. We handed over the otter to be stored in the freezer (already holding three or four others from the Christmas period). I asked when the otter would be sent to Cardiff and whether it was usual for the freezer to be so full at this time of year. Sue replied that the winter months (especially December through to March) are often subject to a peak in otter deaths (largely as a result of road casualties). A likely reason for the particularly high number of winter roadkill is that the rising water levels and rapid currents cause otters to abandon their usual routes under bridges and use alternative routes over roads. Since otters are not particularly roadwise (worsened by their largely nocturnal habits and therefore poor ability to sense car headlights), these diversions pose extremely high risks. Sue added that because so many dead otters had been found over the last few months, the Cardiff freezers were currently too full to receive any new additions, and it might therefore be a while before the otter could be sent for post-mortem analysis.

Although the death of any otter is obviously undesirable, ironically it may be that this high death toll reflects the species' recovery from the population crashes seen in the late 1950s onwards. These population declines largely occurred in the central-western part of the species' range (including the British Isles) and were attributed to water pollution, habitat degradation, declining food resources, road traffic mortality and hunting (Mason & Macdonald, 1986; Macdonald & Mason, 1994). A major cause of water pollution and subsequent otter decline was the presence of bioaccumulating organochlorine/organochloride contaminants, especially PCBs (polychlorinated biphenyls) (Smit et al., 1998), but also pesticides such as dieldrin and DDT (Dichlorodiphenyltrichloroethane) (Mason, 1989). Fortunately, PCBs are now recognised as environmental toxins and classified as persistent organic pollutants; in 1976 a law was passed for their use to be restricted to closed systems in the European Community. The reduced presence of PCBs in the environment means that the average levels are no longer likely to negatively impact otter populations (Mason, 1998).

Owing to the relatively recent declines and slow recovery, the Eurasian otter is protected under the Wildlife and Countryside Act (1981) and is listed as a Biodiversity Action Plan (BAP) Priority Species. Additionally, the Eurasian otter is classified as 'Near Threatened' in the IUCN Red List of Threatened Species. It is hoped that the research undertaken on dead otters will increase our understanding of these fascinating animals and thus improve conservation efforts, reducing the species' likelihood of re-entering the IUCN's 'Vulnerable' category.

Along with the otter, we handed over an envelope containing some photos of the otter in situ, a scanned section of an Ordnance Survey map to pinpoint where I had found it, and a form detailing any other relevant information (see below):

The Environment Agency recording form used for all dead otters. Note that the location details have been eliminated because the species has a protected status (to reduce the potential risk of targeted persecution of other local otters).

According to their latest newsletter (September 2017), the CUOP have now received a total of 3126 otters, 170 of which were acquired over just four months (April - August 2017). The vast majority of the CUOP's otter post-mortems (generally exceeding 80% annually) reveal that the animals have died as a result of road traffic collisions. However it should be noted that we are more likely to find roadkill than otters which have died from other causes such as drowning. The CUOP's February 2013 newsletter stated that drowning was the second most common cause of death (after road accidents), resulting in a total post-mortem incidence of 4.2%. Half of the otters drowned prior to February 2013 were caught in crayfish or fyke nets since the funnel-shape of the nets means that the entrance is wide enough for an otter to swim into but too small for them to escape. In order to prevent such tragedies, it is a legal requirement for those using crayfish or fyke nets to fit an otter guard to the trap entrance and have the relevant permits from the Environment Agency. Read the Environment Agency's Eel Net and Fish Trapping Standard Authorisations Conditions for more details. Otters are a legally protected species and killing them may result in a fine of up to £5,000 or six months in jail.

A fyke net, typically used for catching eels © Copyright Chris (2004).

A dead otter in an illegal crayfish net © Copyright Wildlife Guardian (2015)

Occasionally, there are reports of these illegal crayfish and fyke nets in the Cambridgeshire and Norfolk Fens. Of course some of these traps may have been set naively, without any intention of harming otters; sadly however, the majority of the nets lack otter guards either due to negligence or because they have been installed with the intention of targeting otters (to reduce fishing competition).

These traps are often difficult to find since they tend to be fully submerged along the edges of watercourses and weighed down using heavy objects such as rocks. If the traps are being used illegally, fishermen will not want to draw attention to them by using markers, but they are usually located opposite or adjacent to distinct landmarks such as a house or tree to enable relocation.

If you find a trap that you suspect has been set illegally please contact the Environment Agency’s incident hotline on 0800 80 70 60.

What to do if you find an otter

If you find a dead otter please contact the relevant organisation dependent on the otter's location:

• England     Tel: 03708 506 506 (Organisation: Environment Agency) - ask for the nearest Conservation or Biodiversity Officer).
• Wales         Tel: 0300 065 3000 (Natural Resources Wales) - ask for the nearest Conservation or Biodiversity Officer)
• Scotland    Tel: 01471 822 487 (International Otter Survival Fund)

The relevant organisation will ask you to fill out a dead otter recording form before storing the corpse until it can be transported by courier to Cardiff University for post-mortem examination. If you provide your contact details on the form, a few months down the line you will receive a post-mortem report detailing the cause of death etc. of the otter.

If you find any other dead wildlife, you can submit your records at wildcoms.org.uk or ProjectSplatter.co.uk to enable improved wildlife research and the mitigation of roadkill.

To learn more about the CUOP's work, I recommend subscribing to their quarterly newsletter and watching a video narrated by Dr Elizabeth Chadwick of Cardiff University.

For further reading, check out Hans Kruuk's 'Otters: Ecology, Behaviour and Conservation' (available online here).

References:

Kruuk, H., 2006. Otters: ecology, behaviour and conservation. Oxford University Press.

Macdonald, S.M. & Mason, C.F. 1994. Status and Conservation Needs of the Otter (Lutra lutra) in the Western Palearctic. Nature Environment 67. Council of Europe, Strasbourg.

Mason, C.F., 1989. Water pollution and otter distribution: a review. Lutra, 32: 97-131.

Mason, C.F., 1998. Decline in PCB levels in otters (Lutra lutra). Chemosphere, 36(9), pp.1969-1971.

Mason, C.F. & Macdonald, S.M. 1986. Otters: Ecology and Conservation Cambridge University Press, Cambridge.

Sterry, P., 2010. Collins Complete Guide to British Animals: A Photographic Guide to Every Common Species. 2nd ed. HarperCollins Publishers Limited, UK, pp.136.

Smit, M.D., Leonards, P.E., de Jongh, A.W. and van Hattum, B.G., 1998. Polychlorinated biphenyls in the Eurasian otter (Lutra lutra). In Reviews of environmental contamination and toxicology (pp. 95-130). Springer, New York, NY.