Saturday, 28 February 2015

Lizards 2: Blue Spiny Lizard

Blue Spiny Lizard
One of the more obvious lizards as you enter the reptile house at Bristol Zoo are the various members of a colony of Blue Spiny Lizards, Sceloporus serrifer cyanogenys. Also known as swifts or fence lizards, there are more than 90 described species of Sceloporus found in North America south through Mexico down into northern South America. There is a certain amount of debate around the taxonomy of the various Sceloporus species – some seem to intergrade with others and several species are divided into multiple subspecies.

Spiny lizards are mostly terrestrial, and are especially fond of rocky areas where there are crevices and holes to hide away in. They are also very fond of basking, and there alternative name of fence lizard derives from their habit of seeking out fence posts to bask on. This habit of course exposes them to predation, especially by some raptors and other birds such as the Loggerhead Shrike, a predatory passerine with the odd habit of impaling large insects, lizards, and other prey on thorns to keep them as a larder for later. To avoid this fate, Spiny lizards are alert and agile, and if they feel threatened will rapidly dart for cover or leap away from an approaching predator. They are also partially protected by the rough scales that give them their name, although these are probably most effective when the lizard is wedged in a crevice. If grabbed by the tail, like many lizards they can shed part or all of their tail and get away otherwise unharmed.
Loggerhead Shrike
Their agility also helps in catching their food, which mostly consists of insects. Different species of spiny lizard target different insects, but the Blue Spiny Lizard seems to prefer flying insects. At the zoo they are fed a variety of insects, but sometimes they are given flies, and they are capable of catching these in mid-air after leaping from a rock.

Reproduction in spiny lizards is ovoviviparous. The females give birth to up to 11 young at a time, depending on the age and size of the female, and last year there were several litters born at the zoo. The young grow quickly, and can breed at 1 year old, at least in captivity, so their numbers have to be regulated carefully by separating males and females. Males especially can be quite territorial, so this is also a management issue that needs to be monitored.

Another important feature of their care is ensuring that they have sufficiently hot basking spots so that they can regulate their body temperature, and the correct kind of lighting. As sun loving lizards they need a high UV level in their lighting, or as with many other reptiles they will experience metabolic bone disease.

With such a large range, and with no real human threats to face, they are currently listed on the IUCN Red List as Least Concern. Most of the other Sceloporus species share this status, but there are one or two with restricted ranges or confined to islands which are listed as Vulnerable or Endangered.

Next week, a lizard which has featured in many Westerns as part of the scenery – the Chuckwalla.

(Shrike photo from Wikipedia, lizard my own photo)

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