Mammals seen in British waters

The relatively small islands of Great Britain can boast a coastline that stretches for more than 10,000 miles due to all its “ins and outs” and the huge number of even smaller outlying islands. The coasts therefore provide environments for a variety of sea mammals, especially in the more remote areas where food is plentiful and human interference less so. Mammals that can often be seen from the shore, or better still from a boat, include:

Seals

Grey seal (Halichoerus grypus), also known as the Atlantic seal

Male seals can reach 8 feet in length although the females are smaller. As might be expected, they have dark grey skin although with patches that are light grey or brown. During the breeding season, which is late autumn and early winter, huge numbers can be seen in many locations around the coast, such as the Farne Islands of Northumberland where up to 6,000 individuals congregate. At other times they can be seen resting on remote beaches. The British Isles are home to about half the world’s population of this species.

Common seal (Phoca vitulina)

The common seal is smaller than the grey seal, with males being up to about six feet in length. The skin color is lighter than that of the grey seal, being greyish brown with darker spots, and the face strikes the viewer as being generally “friendlier”, although the appearance of a smile on its features cannot be taken as meaning anything in human terms! It is also known as the harbor seal, and individuals can sometimes be seen in harbors and inlets with the head bobbing in the water. It is also seen basking on sand banks and mudflats with head and tail raised off the ground.

Cetaceans

Common porpoise (Phocoena phocena)

Also known as the harbor porpoise, this is the smallest sea mammal seen in British waters, at around five feet in length. It is dark grey above and light grey below, and can be distinguished from the dolphin by its blunt head, lack of beak, and triangular dorsal fin. It swims in family groups but individuals are often seen on their own.  The south-west coast of Wales is a good place to see them.

Bottle-nosed dolphin (Tursiops truncatus)

This is the sea mammal that most visitors to Britain’s shores want to see as it swims at speed just ahead of motor boats or leaps spectacularly out of the water. Its reputation for friendliness is greatly helped by its smile-shaped snout, but it does indeed seem to enjoy human company. Dolphins grow up to nine feet in length and have athletic, streamlined bodies that are generally grey but with a lighter underside. It has a pointed dorsal fin, the rear edge of which is curved in a sickle shape. Whether the snout is really shaped like a bottle is a matter of opinion, but it is certainly distinctive. Dolphins fish in groups, and a gathering of gulls overhead is often a good sign that dolphins are around.

Minke whale (Balaenoptera acutorostrata)

Whales are far less commonly seen than seals, porpoises or dolphins in British waters, and unfortunately this happens most often when individuals or small groups become disorientated and beach themselves on the shore. However, one species that is seen quite often, especially around the northern and western islands of Scotland, is the minke. It is up to 28 feet long, with a dark back and lighter underside, including a light grey stripe across the flippers. It is a baleen whale, which means that it takes food, including krill and small fish, by straining seawater through bony plates across the mouth that act like a comb. Minkes are usually seen alone but groups may be seen as they migrate between their breeding and feeding territories.

This is by no means a complete list of cetaceans that are seen in British waters, as more than 20 species of whale, dolphin and porpoise are either natives or regular visitors. These include the massive fin whale (up to 80 feet long) and the orca, which gains its unfortunate alternative name of killer whale from its predation of smaller sea mammals such as porpoises and seals.

Mention might also be made of the sea otter (Lutra lutra), as it is a mammal that is often seen on Scottish coasts where it hunts for fish and plays among the rocks. When the water is calm, an otter will lie on its back eating its latest catch. However, this is the same species as the animal that is seen on inland rivers throughout Great Britain and should therefore be described as a “mammal that lives by the sea” rather than a “sea mammal”.

A visit to the British coast, especially away from the main population centres, is usually a rewarding one in terms of wildlife sightings. Sea mammals can be particularly impressive, although it should always be remembered that one is there to observe and not interfere. Getting too close to a seal colony, for example, can be dangerous and is not recommended. These are wild animals that have every right to be where they are and to continue their lives undisturbed by gawping tourists.

© John Welford

Lesser trefoil

Lesser trefoil (Trifolium dubium) is one of several wildflowers that has been suggested as the original “shamrock” used by St Patrick to explain the nature of the Holy Trinity to the people of Ireland. A direct translation of “seamrog” is “little clover”, which could describe a number of plants, so the claim of lesser trefoil must be set alongside those of white clover, black medick, wood sorrel and even watercress.

Lesser trefoil is commonly found in most parts of Great Britain, the exception being northern Scotland. It is a plant of pastures and grassy banks. It is a low-growing downy plant that can reach a height of 20 inches (50 cm). It flowers from May to October.

As the name suggests, lesser trefoil has leaves that divide into three leaflets. The many flower-heads produce anything from ten to 25 tiny yellow flowers, the narrow upper petals of which have their sides folded together. When the flowers die, the petals do not fall from the plant but remain attached as covers for the straight brown pods that contain the seeds. These look a bit like the heads of hops, which is why lesser trefoil is counted as a “hop trefoil”.

© John Welford

Humans or insects: who's doing better?

An impartial observer from another planet might soon deduce that it was insects, rather than human beings that constituted the most successful form of animal life on Planet Earth.

Just look at the facts:

There is only one species of human, but possibly as many as eight million insect species that have evolved to fit just about every habitable zone on the plant.

Humans have been around for no more than two million years, but the fossil record shows that insects were around hundreds of millions of years ago. Modern cockroaches, for example, have changed very little from their ancestors that lived 300 million years ago.

However, some species have undergone considerable change – fossilised dragonflies have been found with wingspans similar to that of a modern seagull.

Here are some other remarkable facts about insects:

Although there is a huge range of butterfly species, there are ten times as many species of moth.

The world’s smallest insect is the fairyfly, at 0.2 millimetres across – about the size of the dot on the i of “insect”!

Silkworms (which are not worms but insects) are no longer found in the wild but have been completely domesticated as producers of silk.

© John Welford

Hawaii's silent crickets

It is well known that male crickets attract females by “singing”, which is actually a sound made when they rub their wings together. This works because the wings have ridges and bumps that scrape against each other. Without those rough bits there would be no “song”.

So why have the oceanic crickets (Telogryllus oceanius) on Kauai and Oahu (Hawaii) lost these ridges and are therefore no longer able to sing?

This is an example of evolution that appears to have worked to the disadvantage of a species. If the males cannot attract females how can they procreate?

The problem for the crickets was that the singing did not only attract female crickets but also a parasitic fly with the botanic name Ormia ochracea. These nasty little beasties laid their eggs on the crickets and, after hatching, the larvae proceeded to eat the crickets alive.

The crickets with the quietest songs – due to having less prominent wing ridges - stood a far better chance of surviving these assaults and so managed to father the next generation of crickets. Their offspring would also tend to have smoother wings, and thus be able to pass on the “flat wing” gene.

The net result has been that 95% of the island crickets now have completely flat wings and make no sound at all when they rub them together.

This is a fascinating example of how evolution works. The original process of developing ridges and bumps would have worked to ensure that the strongest singers produced more offspring, but now the opposite is the case.

There are two very interesting aspects to this story. One is that the male smooth-winged crickets continue to rub them together vigorously despite producing no sound whatsoever. It is a behaviour that is so deeply ingrained in their genes that they have no choice but to produce silent songs!

The other question is: if the male crickets can still attract females – which they obviously can – why did they need to sing in the first place? Presumably the answer to that is that evolution will always favour the strongest members of a species, and that strength will therefore be passed down the generations, but when that strength becomes a liability, weakness itself becomes a strength!

In other words, although the best adapted members of a species will always attract the most mates and produce most offspring, that does not always mean that the less attractive members will fail to reproduce. If the strong specimens are removed from the scene, the weak ones will come to the fore.

Maybe this is an example of “In the country of the blind, the one-eyed man is king”!

© John Welford

Crocodile jaws: their one-way strength

You do not want to get the wrong side of a crocodile or alligator, and by the wrong side I mean inside its jaws as opposed to outside!

A dog bite is unpleasant enough – I should know, as I bear the scars from the attentions of a German shepherd dog a few years ago! – but a dog can only snap its jaws shut with a force of 100 pounds per square inch. This is enough to cause a nasty injury to the top of one’s finger, but a croc could easily remove the whole hand, given that its jaw can exert a force of 3,000 pounds per square inch.

Any small creature that is unfortunate enough to be snapped up by a crocodile is highly unlikely to see daylight again, its bones being crushed to pulp in no time at all.

However, despite the immense strength of the muscles that close a crocodile’s jaw (the same applies to alligators and caymans), those that open the jaw are considerably weaker. This means that it is possible to escape being eaten as long as one can prevent the jaws from opening in the first place, and this can indeed be done. It has been suggested that some people would be able to hold a croc’s jaws shut with just one hand – presumably quite a large one!

The so-called sport of alligator wrestling has taken advantage of this fact, although wrestlers have also to beware of the gator’s practice of spinning round at speed to rip pieces off its larger prey when it has managed to grab hold of a leg, for example.

Wrestlers will hold the alligator’s jaw shut and then turn it on its back to stroke its underside, which will sent it to sleep. There is then a bit of trickery to pretend that the beast is fighting back, purely for the sake of making the wrestler look even stronger and braver than he really is!

© John Welford

Bottlenose dolphin

Dolphins that are kept at marine life centres and entertain the public are almost always bottlenose dolphins. There are two species – Tursiops truncates, which is found in oceans across the world, and Tursiops aduncus, which is smaller and is found off the coast of India and in the western Pacific. It is possible that more species may be defined in future, given the variations in size and appearance that can be seen in different regions.

Lengths of fully-grown adults vary from 1.9 to four metres (6.25 to 13 feet). The shorter specimens, found around tropical coasts, have relatively large pointed flippers, tail flukes and sickle-shaped dorsal fin, whereas the much larger dolphins found in open oceans have proportionately smaller extremities.

The basic coloration of the bottlenose dolphin is a dark grey or black back, fading to cream on the underside. However, there are many variations in actual colouring and markings between individual animals.

There are also many variations in social groupings, as between small and large groups and in feeding methods, given that some groups appear to hunt in packs by herding and trapping their prey. The calls and sounds emitted by bottlenose dolphins are also varied across the geographical range as are the water-slaps and leaps that they display.

The chief defining feature of the bottlenose dolphin is its short and robust beak, its “bottle nose”, that contains up to 27 pairs of small, conical teeth. These are used to take many kinds of fish, molluscs and crustaceans.

The shape of the bottlenose dolphin’s mouth and beak give the impression that it is always smiling, but it is important not to be too anthropomorphic about this – one should always beware of ascribing human emotions to wild animals. It is this mistake that has probably led to so many bottlenose dolphins being enslaved to entertain gawping tourists.

© John Welford

A short guide to invertebrates

Invertebrates are animals without backbones, and they represent about 90% of all living creatures.

Three major invertebrate groups are arthropods, annelids and molluscs.

The bodies of arthropods are protected by a hard outer skin known as an exoskeleton. Their bodies are usually divided into segments. There are four main arthropod groups:

Insect bodies have three segments, namely head, thorax and abdomen. Three pairs of legs are attached to the thorax as are the wings if the insect species has them. Sensing antennae, as well as eyes, are on the head.

Crustaceans have two pairs of antennae and eyes on stalks. Although most crustaceans live in water and breathe through gills, there are some land species such as woodlice.

Spider bodies have two segments with four pairs of legs. Some species have more than two eyes. Many spider species are able to produce silk from which they construct webs.

Millipedes and centipedes are multi-segmented arthropods, the distinction between them being that centipedes have one pair of legs per segment and millipedes have two pairs.

 Annelids are segmented worms, with each segment containing a complete set of organs. Most worms burrow into the soil.

Molluscs have soft bodies and no skeleton, although many species are protected by a hard shell. They include octopuses and squids at sea and garden snails and slugs on land.

© John Welford