Very few land mammals made it across to the Outer Hebrides and many species common on the mainland such as Foxes, Badgers, Stoats and Weasels don’t live on the islands at all. What the islands lack in land mammals they certainly make up for in marine mammals.
Worldwide there are 13 extant species of otters although there is just one species found in the UK which is the only one in Europe, the European Otter (Lutra lutra). Otters require freshwater to maintain the quality of their fur which helps insulate the animal whilst out fishing. Although reliant on freshwater it readily adapts to a marine environment as there is often a more abundant supply of food.
The Outer Hebrides have a thriving Otter population as there is so much habitat for them. Miles of coastline indented with narrow inlets, plentiful rock pools full of seaweed and lots of freshwater lochs and burns. Fresh water is very important to an Otter as although they may depend on the sea for the majority of their food they need to keep their coat in superb condition. To do this they must wash regularly in fresh water to clean out the salt and maintain some water repellent qualities.
The best time to see Otters is when the cubs are out and about with their mother teaching them how to fend for themselves. The cubs spend the first few months in their natal holt before venturing out but when they do they regularly keep in touch with their mother by calling. The call is sharp, high pitched pipit-like note that could be easily over looked as a small bird but once known is an excellent way of locating Otters. The best time to look for Otter appears to be during the autumn and winter. Why they should be more easily found at this time of year could be due to a number of things such as the higher demands and greater need for regular feeding during the harsher winter or may just be that fewer people are out so there is less disturbance.
Two species of seal can be found around the islands, the Atlantic Grey Seal and the Common Seal, or Harbour Seal as it is alternatively known. Both these names are descriptive and tell you a little something of how to identify them. Grey Seals are largely dark grey although occasionally they are paler or russet in colour they tend to be less variable than Common Seals which are often intricately spotted helping them blend into rocks.
As adults, Grey Seal have a large 'Roman' nose which leads to them occasionally being known as horse heads. Both males and females show this distinctive head shape although it is more pronounced in the bulls.
Common seals on the other hand are much gentler looking and appear to have a head resembling a Golden Retriever. They also frequently adopt this characteristic 'banana posture' that Grey Seals don't hold so much or for any length of time.
Another clue lies in their name; Harbour Seals frequently haul out on sand bars and in very sheltered inlets whilst Greys are often encountered on smaller off-shore islands in more exposed locations. This or indeed any of the points above are not fool proof as young of both species closely resemble one another. The only sure way is to look at the shape of the nostrils when they are closed. Common Seals' nostrils form a V or a heart shape whilst Grey Seals are more parallel. It takes a bit of practice but given good views and closed nostrils, most can be readily assigned to a species.
The waters around the Western Isles / Outer Hebrides are excellent for whales and dolphins with a number of companies around the Inner Hebrides offering tours to see this group of mammals in their natural habitat; the sea. No such tours operate from the Outer Hebrides although there are a number of land based locations and ferry journeys that will reward those that put some time in looking for cetaceans. The following ferry journeys can be excellent in the summer months although you may spot whales or dolphins at any time of year:
Oban - Lochboisdale, S Uist / Barra. Good for Common Dolphin, Porpoise and Minke Whale as well as Basking Sharks from July - September. Pilot Whales are also occasionally reported as well as Risso's Dolphin, Bottle-nosed Dolphin and the odd Orca.
Uig, Skye - Lochmaddy, N Uist. A shorter crossing than the one above but never-the-less can be good with regular sightings off Vaternish Point, Skye including Bottle-nosed Dolphins, Common Dolphin, Porpoise and Minke Whale. Orcas are very occasionally seen.
Ullapool - Stornoway. Excellent in calm conditions with a good chance of Risso's Dolphin, Common Dolphin, Porpoise and Minke Whale.
Inter-island crossings can also be productive with regular sightings of Bottle-nosed Dolphins in the Sound of Barra with Porpoise and the odd Minke Whale in the Sound of Harris.
Land based observations are limited in the southern isles although the sea watching locations of Ardvule, S Uist and Aird un Runair in N Uist can be good for Porpoise and Minke Whale. The small cliffs at Scoplaig / Griminish Point produce regular sightings and is probably one of the better locations due to the deep water trench coming close inshore here.
There are many potential locations in Harris and Lewis for observing cetaceans although a few stand out as being excellent such as: the lighthouse on Scalpay to the east of Tarbet, NG247947. In Lewis: Tiumpan Head, NB 574378 and the Butt of Lewis are the best known locations although there may also be potential on the western headlands Mangersta, NB 004334 and Gallan Head, NB 052394. Tiumpan Head has had a dedicated, small team of watchers since at least 2012.
Regular species sighted: Harbour Porpoise, Bottle-nosed Dolphin, Risso's Dolphin, White-sided Dolphin, White-beaked Dolphin, Common Dolphin, Minke Whale, Killer Whale.
Rare sightings of Humpback and Fin Whale have also been recorded in the last few years. The frequency with which Sperm Whales are also washed up may mean that this species is also a contender along with the odd beaked whale. A bit of effort would no doubt reap some excellent rewards, after all a major whaling station operated out of Harris in the past.
Red Deer is the only species of deer you will see on the islands and apparently an old introduction here. It occurs throughout the main islands of Lewis, Harris, North Uist, Benbecula and South Uist. They can also be found on many of the smaller islands around North Uist as they regularly under take crossings to these quieter uninhabited spots being good swimmers.
Unfortunately some of the introductions have caused problems. Hedgehogs can be found on all the main islands and were probably originally introduced to control slugs but also have a taste for birds eggs. Studies of waders nesting on the machair in South Uist have found that Dunlin, Ringed Plover and Redshank have all suffered significant losses to these animals. Another alien to the islands and Britain, the Mink has also had devastating affects on the wild birds. Mink are veracious hunters and have caused huge problems at some of the tern colonies. Mink have been virtually eradicated from the Outer Hebrides although occasional sightings result in an intensive trapping campaign in an attempt to eliminate them completely from the islands.
Mountain Hares can be found on the northern isles of Harris and Lewis and rabbits throughout. Rabbits were introduced in Medieval times and although they can prove a pest, they probably display more benefits than not, as they are a food source for many birds of prey and provide ready dug burrows for Puffins as well as turning and aerating large areas of soil.
The smaller denizens include both Brown and Black Rats, although the latter is found only on the Shiants a scheme has been introduced to eradicate them from the latter island to enhance the site for breeding seabirds. Long-tailed Field Mouse or the Wood Mouse as it is alternatively known is common as is the Short-tailed Field Vole in the Uists. Voles are absent from Lewis and Harris which undoubtedly contributes to the lack of Short-eared Owls here. It is thought that both these two rodents were also introduced although when this happened and how is a mystery. Other small mammals include Britain's smallest, the Pygmy Shrew.
In and around Stornoway there are a few scattered colonies of Pipistrelle Bats. There are at least two colonies in the town and others at both New Market and Lochs, Lewis. Occasionally bats may be found away from these core areas although they are rare and not resident. There is one record of what is thought to have been a Noctule Bat and was either this or a Leisler's Bat.