Over the years I have heard stories of otter sightings in Bristol. I love otters, I tend to melt into a gooey puddle of ‘squee’ when I see them at zoos, but I have never actually seen a wild otter in the UK and until recently had no idea where, when or how to see them or signs that they had been somewhere.
In May 2019 I attended a one-day Otter Survey Training course run by Gwent Wildlife Trust at the beautiful Magor Marsh reserve. The course was led by Jeff Chard (the Otter Man) and ecologist Lee Jenkins. The morning started with an introduction to otters, and in the afternoon we had a walk around the reserve looking for otters or signs of. Unfortunately, we did not see any otters themselves, but we did find plenty of signs of them around!
Otters in the UK:
Our native otter, the Eurasian otter (Lutra lutra), is the only otter species in the UK. It is a mustelid, like the badger, that has lived here since the last ice age. Their popualation enjoyed a boom over the previous 10,000 years; however, they have been in decline since the 1950s due to industrialisation, pollution, pesticide use, persecution in human/wildlife conflict (i.e. fisheries and pond owners), and hunting. Fortunately, their modern protected species status and cleaner rivers means that they are somewhat making a come back. They are an environmental indicator species; if there are signs of otter this indicates that the water quality is optimal and pollution levels low. They are very elusive, however, so it is difficult to accurately gauage their current population and usually you can only see signs that they have been there, though there are increasing sightings of otter in urban areas, in rivers or even crossing roads. Sadly, this has led to several road fatalities and since 1992 3,000 carcasses have been handed over to Cardiff University Otter Project for post-mortem study, many of which are road fatalities.
Otters and the Law:
As mentioned, they are a protected species in the UK, fully protected as a European protected species (EPS) and is also protected under Sections 9 and 11 of the Wildlife and Countryside Act 1981. This means you will be breaking the law if you:
- capture, kill, disturb or injure otters (on purpose or by not taking enough care)
- damage or destroy a breeding or resting place (deliberately or by not taking enough care)
- obstruct access to their resting or sheltering places (deliberately or by not taking enough care)
- possess, sell, control or transport live or dead otters, or parts of otters
If you’re found guilty of an offence you could get an unlimited fine and up to 6 months in prison. [Source]. All of this includes accidentally disturbing otters when trying to see or photograph them, including leaving a trail camera, so it is important to remember this!
About the Otter:
Lutra lutra is a semi-aquatic crepuscular (mostly active at dusk and dawn) mustelid. They have brown fur with a mean hair density of 60,000-80,000 hairs/cm2 in two forms: an upper guard hair and a lower wool-type hair [Source]. Each individual has a unique “moustache” which, with a good quality photograph, can aid in individual identification. They have long, slender bodies, and are probably much larger than you would expect, being closer in size to a badger with males at ≥1.4 m long; body ≥95 cm, the rest being made up by their long, thick tail. Despite this, they are often confused with the much smaller non-native American mink. Males weigh in at approximately 8.2 kg and females approximately 6 kg.
Their lifespan is up to 10 years, though in the wild they rarely survive beyond 5 years. They can breed year-round, having litters of one or two cubs each time, which the female raises alone.
They have five toes, which are webbed, although only four toes may be visible when looking at a footprint as one toe is slightly higher than the others. The images below are of casts of footprints, provided by Jeff Chard and Cardiff University Otter Project (photos my own).
When they dive under water their facial muscles close the ears and nose to prevent water flooding in, this also changes the shape of their eyeballs enabling them to see underwater. It is thought that diving may induce bradycardia as it does in seals and other diving mammals, this is a slowing of the heart rate when diving to preserve limited oxygen reserves, and they can remain submerged for four to six minutes.
The below images of an otter skull show their large orbitals, wide cranium, and thin mandibular region and nasal bridge [skulls courtesy of Jeff Chard and Cardiff University Otter Project, photos by me].
Otters will spend ≥ 65% of their time resting, which they will do either in their holt (their ‘den’) or on ‘couches’ of flattened vegetation. Males will travel up to 50 km and females up to 20 km, though both may go much further than this! They may have multiple holts, the one used depends on environmental factors, if the environment changes they will move holt. They will scent guard their territories by leaving spraint, urine and anal jelly in prominent places. These provide valuable hormonal markers advertising their territory boundaries and breeding status.
Surveying for Otters:
When surveying, first pull up a map of area and learn the topography. Survey approximately 2 km beyond your assigned survey area in either direction and make sure you mark on your map each and every sign of otters you have found. Good places to look for signs of otter include bank sides, small riparian caves, trees, log piles, reed beds, crooks of pollarded trees, brambles and blackthorn hedges. A pair of binoculars may be helpful to see the opposite side of the bank or to scope out potential holts or couches from a distance so as not to disturb any potential otters. Holts and couches may not be right next to the bank, however, so make sure you look carefully in the surrounding area too.
Urine: Check moss patches for yellowing, as this may indicate urine burn.
Spraint: When looking for spraint, be prepared to look higher up than perhaps you would imagine and to get down and dirty and sniff the spraint! Spraint has a very distinctive smell, not unlike jasmine tea; once you have smelled spraint you will never mistake it for faeces of another animal, but it does mean if you encounter something that looks like otter spraint but isn’t, you may get a slight shock when you are expecting that sweet jasmine smell and instead get a nose full of strong musk and definitely not otter spraint! Spraint will be full of small bones, fish scales, and invertebrates; when it is fresh is a dark brown, almost black, colour which gets lighter and greyer as it ages. If you take a sample of the spraint, ensure you do not take all of it. Females with cubs will reduce spraints to reduce the chance of detection.
Anal Jelly: Anal jelly may be a variety of different colours: yellows, greens, and browns etc. and may or may not be found alongside spraint.
Footprints, claw marks and tail marks: Look out for footprints, claw marks and tail marks, and when photographing their prints try to include something to use as a scale, like a coin or ruler. Don’t forget to look higher up than you would expect, as they may also climb over fencing or other obstructions to get where they want to be. With that said, however, remember that when travelling from A to B, otters prefer to take the ‘path of least resistance’.
Discarded food: You may also spot half-eaten fish, scales or bones, crayfish parts, and even frog or toad skins and innards, another good indication that an otter has been in the area.
Important note: An absence of records does not mean an absence of otters! It is important to record and report all signs of otter, even if the otter itself has not been seen.
Otter Surveying in the Future:
Only a few days after taking part in this course I was walking along the River Frome in Bristol and keeping my eyes peeled for signs of otter, when what should I see but some otter spraint! I have found spraint at this same site multiple times since, which I reported to the Greater Bristol Otter Survey Group and I have been invited to do regular monthly surveying at a different site in Bristol. Exciting!
Although I still have yet to see an actual wild otter, this is a positive step in the right direction toward seeing one. It is important to survey for otters to monitor their popuation and quality of our rivers, and the monthly surveying and future refresher training days will help to keep my otter survey skills fresh in my mind.
Further reading about otters:
Otters: Ecology, Behaviour and Conservation (Oxford Biology) – Hans Kruuk