In the first of a new series of posts about “How to Look for Mammals“, I take a look at one of our semi aquatic species, the Eurasian otter. The Eurasian otter is distributed across Europe and into Eurasia, but it is absent and restricted to small isolated pockets in some European countries, but it is slowly starting to make a recovery across Western Europe. A claim to fame for Ireland is that it is actually a stronghold for the otter, and marks the western most point of the otter’s distribution. It is thought that the Irish climate with lots of fresh water makes it an ideal habitat for the otter.
Otters are protected under Annex IV of the European Habitats Directive, making it illegal to interfere with an otter’s breeding or resting place. Ireland and other EU member countries are obliged to report on the national status of otters every few years, and this information is collected, analysed and reported on during the “National Otter Survey“. As otters are shy animals, they are difficult to directly observe, hence otter surveyors rely upon otter field signs to inform their presence or absence. The most recent Irish survey was published last year by Reid et al. where the Irish otter population was reported to be of ‘favourable‘ conservation status, despite a 23% population decrease reported between the 1980’s and 2005/2006. It is possible that previous studies had incorrectly reported a downward population trend due to the imperfect nature of the survey strategy. I discussed this in another post “Calling into question the accuracy of the ‘Standard Otter Survey’“.
In search of otters
Due to the imperfect nature of otter surveying I suggest the following: If you don’t spot signs of otters on your first outing, never presume this implies their absence as you may have visited after rain, might have overlooked their signs, or the width of the river and lack of obvious sprainting sites (otter poo places) might have simply impaired your ability to observe their clues. With these complications and inaccuracies in mind, the signs and clues I’ll discuss below are simply a guide and illustration of some of the tips and tricks that might increase your chances of spotting otter activity.
Looking for otters on the coast
We’ll start off at the coast. This is where otters tend to be most abundant due to the higher availability of food in the coastal areas. Otters here are feasting on crabs, eels, eelpout, some salmonids, bullrout and other small fish species. They are not strict fish eaters however, and they’ll also feed on birds, small animals and invertebrates; they are in essence opportunists! On a slight side note, I have on occasion been asked if the otter found in the sea in Ireland is a different species, and no it isn’t, the same species is found at both at the coast and inland. In the Americas, there are river and sea otters that are separate species, but here in Europe it is the same one.
If I’m at a beach or cove, the first thing I look for is the presence of a stream or river. Otters that have been swimming in the sea have to wash the salt water from their fur, so the presence of fresh water on the coast is an important indicator that otters may be present. If there is a fresh water source at your site, this is the most likely place where spraints (otter poo) will be found. Otters mark their territory with spraints as a way to communicate and send messages to other otters. Otters use features in the landscape that stand out making structures like bridges key places to find spraints. If water levels are low, otter footprints may be seen beneath the bridge on sandy banks and ledges. Other places to search are rocks and boulders along the stream, especially ones that tend to crop out. If it catches your eye, it may also catch the otter’s attention. Bear in mind that tidal waters wash away otter activity, so otters also place spraints on higher points above the reach of the tidal waters.
If the stream or river has a bank, it is worth checking along here for little tracks along the grass. Along these tracks, otters may leave spraints on grassy ledges or tussocks, which can sometimes be detected from a short distance as regular sprainting sites may leave the grass a darker shade of green or even yellow due to effects of sprainting and urinating. Along these areas, you might also see the remains of previous meals such as the bits of crab shells or large fish bones, that the otter wasn’t brave or foolish enough to tackle.
When the otter makes a return to the stream or river from the bank, they may use the same area, and this spot will get muddy and slightly eroded forming an “otter slide”, another feature to look out for. It is also worth noting tracks or a “run” (a little path through the grass) away from the river as these sometimes lead to the otter holt or resting place, where the otter may lay up during the day. A resting place may simply consist of an area of flattened grass, but a holt might be a crevice in the rocks, a burrow type hole well disguised by thicket and other growth. Otters have also been known to use disused badger setts and fox dens as holts.
Further down the coast, towards the sea I tend to keep my search towards a cliff face or rocky area, particularly a place where there may be rock pools. I also search for landscape features here such as rocks, outcrops and grassy tussocks that are all important areas to find spraints. In the absence of a suitable feature, otters may scrape the sand into a mound and spraint on top of that, forming a “sand heap”. A look at caves is always worthwhile, especially towards the back of a cave where older spraints may not have been completely washed off.
Looking for otters inland
Away from the sea, otters will follow rivers and streams in pursuit of their beloved fish. Just like at the coast, otters will use landscape features to spraint or mark their territories. Bridges and rocks are the prime sprainting locations so be sure to check underneath bridges if they are accessible, and the banks near bridges. Again, rain is an important factor, and recent rain may prevent gaining access to a bridge and naturally the spraints get washed away. Be sure not to put your own safety at risk either, if in doubt, stay on the bank. The water levels were very low in the examples I have used below.
Otters in the uplands
I’ve regularly come across otter evidence in the the uplands of the Comeragh Mountains, Co. Waterford. The rivers can be followed to the upland lakes, where otters are especially abundant during the frog spawning season around March. This is when otters gorge themselves on frogs. Other food items they eat in the uplands are salmonids, roach, birds, small mammals and invertebrates.
I change my search tactics in the uplands as the terrain changes considerably from the coast and the agricultural lowlands. The search gets considerably trickier due to the difficult terrain, and there are countless possibilities for otters to spraint and make a holt among the large boulders. There are also generally fewer otters due to a lower prey availability. This makes otter surveying in these areas much more difficult.
Happy otter spotting…
Reid N, Hayden B, Lundy MG, Pietravalle S, McDonald RA, & Montgomery WI (2013). National Otter Survey of Ireland 2010/12 Irish Wildlife Manuals No. 76. National Parks and Wildlife Service, Department of Arts, Heritage and the Gaeltacht, Dublin, Ireland.