13 March 2013 ~ 0 Comments

Who Bothers Hawaii?

waipio valley

Hawaii archipelago is one of those lands suffering not only from human activity, but from alien species as well. For many centuries there were no predators or invasive species that could threat to conventional livelihood of Hawaiian ecosystem.

Long before European settlers, there were only two mammal species distributed over the islands – hoary bats, apparently brought by winds from America, and monk seals. The population of seals declined significantly in the 19th century, as colonists started to hunt them for skin and eat, and to date conservation of monk seals is one of the primary environmental issues on Hawaii.

All in all, the diversity of Hawaiian fauna was enlarged a lot, as numerous species of domestic animals (sheep, feral pigs, wild boars, deer), ants (big-headed and Argentine ants), plants (the Velvet tree) found a perfect place on Hawaii to be dispersed, therefore, signifying about the end of Eden.

Negative Alien Species

One of the recent zoological researches, enclosed by Proceedings of the National Academy of Sciences, featured bees, imported from North-American continent, as invasive and distrustful species on the archipelago.

It is one of the examples of how alien species might modify lifestyle and habits and thereupon cause severe damages for a new habitat. In particular, this research is referred to revived bees’ abilities to consume any variety of food and to form larger colonies.

In normal conditions, Pennsylvania bees gather in small colonies for one season, while on Hawaii they gather in large colonies (about 600 thousand bees) for long-term periods. In this way, bees obstruct essential development of forest areas and sub-alpine vegetation.

Positive Alien Species

However, there some examples of invasive species that promote natural advancement of Hawaiian ecosystem. To be more précise, the biggest achievements are attained by alien terrestrial birds, which include 58 species.

They play an important role in reproduction of many indigenous plants. For instance, birds distribute seeds of Lehua trees (Eugenia plants), known for its reddish wood and bright red flowers.

Unlike native birds, consuming exclusively nectar or invertebrates, alien birds eat fruit of trees and, therefore, disperse plant seeds over the area. This is a nice example of how invasive species cannot just push out the native, but also take on their functions, often coping with them no worse than their predecessors.

Potential Alien Species

For many centuries Hawaiian archipelago was free from reptiles, especially snake species. Notwithstanding in recent years there were some notices about potential threat of snakes’ distribution to the islands, preconditioned by illegal snakes trade and keeping some as pets.

Having no natural enemies, snakes might embed themselves deeply into the Hawaiian ecosystem, if they happen to be out of human control. In this case, the fate of Guam Island is imminent, where imported brown tree snakes ate all the birds and, therefore, caused severe ecological damage.

On Hawaii snakes can eat bird eggs and small chicks, including representatives of 34 species of Hawaiian forest birds at risk of extinction. If birds disappear, there will be more spiders that create webs over the trees and so darken the wood; insect populations may get bigger.

In this case, the list of consequences might be prolonged, eventually ending up in completely new vision of Hawaiian environment.

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16 October 2011 ~ 0 Comments

How To Tell The Different Between Slow Worms And Snakes

 how to tell the difference between slow worms and snakes
Creative Commons License photo credit: anabis

Something long and thin wriggles past you in the countryside. The knee-jerk response may be that you’ve just seen a snake but how can you be certain that what you’ve seen isn’t a slow worm instead? Let’s take a closer look at slow worms and the different species of snake present in the UK to give you a better idea of how to correctly identify and distinguish between snakes and slow worms.

There are a number of factors that can help us to tell the difference between slow worms and snakes. Some are “dead certs” – almost guaranteed to ensure you have the correct identification – whilst others are less certain and in these cases it may be necessary to use a number of different factors in order to be reasonably confident about an identification.

This is especially so if you only had a fleeting glimpse out of the corner of your eye rather than a good long look at the reptile in question. Wherever possible – both to make identification easier and to serve as a reminder in the future – try to take a few photographs of the animal in question.

These don’t need to be “award winning” nature photographs – certainly mine aren’t – but when a creature could vanish at any second grabbing a few quick pictures that you can analyze at your leisure later on can not only make your identifications more accurate but also more enjoyable as you sit and ponder them at a later date in the comfort of your own home.

Body Shape

Slow Worm HampshireWhilst the body of most snakes tends to taper gently from the mid section down to a fine point at the end of the tail the slow worm typically appears far chunkier with the “tail” appearing far blunter and ending far more sharply. In addition, be aware that unlike snakes, slow worms can “drop” their tails like many other lizards and so this can lead to an even “stubbier-looking” tail than normal.

Head Shape

The head shape differs between slow worms and snakes but it can be quite a subtle feature so isn’t recommended as the only identification source. In general the species of British snakes tend to have rather flatter-looking heads than the higher, rounder head of the slow worm. Remember that the slow worm is a lizard and not a snake and when you look closely at them it can be quite easy to see that their head is more lizard-like than snake-like.

Colouration

Grass snakes, smooth snakes and adders all typically have quite clearly-defined patterns to help with camouflage. Spots and stripes are common in these species while the slow worm is typically a reasonably uniform brown in colour. Younger specimens may have stripes of colour but these tend to be longitudinal (from head to tail) rather than the more lateral marking of, for example, an adder.

Prey

British snakes feed on a variety of prey including frogs and small mammals but slow worms are rather different in that they prefer small invertebrate prey. Slugs are a perfect example of the type of food they enjoy and so should you see a “slow worm” eating a frog for example, it’s almost certainly actually a snake.

Eyes

Snakes have sealed eyelids through which they see which makes them appear to have no eyelids. As a result they are also incapable of blinking. As lizards however, slow worms do have eye lids and with patience you may even see them blink. Blinking, therefore, is a guaranteed indicator that what you have seen is a slow worm and not a snake.

Size

Of course baby snakes are smaller than adults but overall slow worms are far smaller than most of the British species of snake. Baby slow worms – which are born live rather than in egg form – can be just a few inches long and even the adult rarely exceed more than a foot. Compare this to the size that an adder or a grass snake may achieve and a smaller-sized, serpent-like creature is more likely to be a slow worm than a snake.

Habitat

Thanks to their preferred prey, slow worms are most likely to be seen after rain and/or in the early evening where they will be searching for small invertebrates to eat. In contrast adders and grass snakes are often seen basking in the heat of the day though a slow worm that has been disturbed from it’s hiding place may still be seen at these times of day.

Adders, generally, seem to prefer heathland habitats, grass snakes those with open water in the form of ponds or streams while slow worms can be seen in a variety of habitats though grassland areas is where they are most often observed.

Conclusion

Telling a slow worm from a snake can take a little practise but hopefully you can see there are a number of factors that you can use to help you make a definitive identification.

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06 July 2011 ~ 0 Comments

Where To See Adders

Adders
Creative Commons License photo credit: Danny Chapman

Adders (or vipers) are the UK’s only venomous snake and whilst quite a degree of fear still surrounds them from people who picture deadly cobras hiding in their garden these snakes are generally shy and retiring. Indeed if adders were easy to find then we wouldn’t need an article like this – we’d all be tripping over them and instead visitors to this site would be more likely to ask how to avoid adders :-)

Like all reptiles, adders are fans of warm, dry weather where they can bask in the heat of the sun before hunting for prey. Cool, damp, grey weather tends not to suit them as well and they may well hide away out of view or – in the winter months – even aestivate to conserve vital energy.

Equally so, the warmer a snake gets the more active it becomes – and as it becomes more active so it also becomes faster moving and so harder to spot. The ideal situation to see adders is therefore early on in the morning of a warm, sunny day in summer. The early hours before the snakes get too active and before they get annoyed by dogs and their owners can be the best time so if you’re serious about seeing adders your best bet is to set your alarm and get up bright and early.

As for habitat, adders tend to prefer dry environments such as heathland and gorse-filled grassland. My latest siting of an adder was one hiding just under a gorse bush up ontop of Cissbury Ring in Sussex a short while ago.

Like most snakes, Adders are very sensitive to vibrations through the ground and so it is best to walk as lightly as possible if you’d like to see them – stomping around in heavy walking boots won’t do you any favours – and I prefer to walk slowly and deliberately in flexible trainers so I step as lightly as possible on the ground.

When seen in photographs adders appear to be quite obvious snakes with a background colour varying from olive green through brown to the common silver or grey over-laced with a dark black zigzag pattern down it’s back. However in the wild these markings can make it surprisingly difficult to see and in the right habitat on the right day you may well pass numerous specimens without even realizing it.

While adders can and do climb, they are most often seen on the ground and in the spring time males can sometimes be seen “fighting” for mates as they stand up high and attempt to “wrestle” other males to the ground.

The other British snakes are the smooth snake and the grass snake. Smooth snakes are now very rare indeed so it is highly unlikely you will encounter one while grass snakes tend to prefer damper habitats such as those with ponds and streams.

Consequently a useful tip for getting an idea of whether there are adders in your local area is to keep an eye out for shed skins in the types of habitats mentioned as these will almost certainly belong to an adder and show some recent activity. To slough a skin an adder will normally rub against a rough object such as an old tree stump or sharp bush so keeping your eyes peeled for these signs can be a good indicator that you are searching in the right area.

Have you seen an adder recently? If so please leave a comment below to let us know when, where and how – we’d love to hear from you!

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30 August 2010 ~ 0 Comments

A List Of Native British Reptiles

 Natrix natrix
Creative Commons License photo credit: anabis

Britain is home to an amazing six species of native reptile which for a climate like ours never ceases to amaze me. Note that one can also see the Green Lizard (Lacerta viridis) on the isle of Jersey though it appears to be absent from the rest of the UK.

The general list of British reptiles is:

– The Common (or Viviparous) Lizard (Lacerta vivipara)
– The Sand Lizard (Lacerta agilis) – now very scarce
– The Slow Worm (Anguis fragilis)
– The Grass Snake (Natrix natrix)
– The Adder (or Viper) (Vipera berus)
– The Smooth Snake (Coronella austriaca) – also sadly very rarely seen these days

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