A Bermuda Skink was recently filmed visiting the CahowCam burrow as we wait for the female to return to lay her egg. Historically, they have a long-standing, important relationship with the Cahows as they help keep the nests clean.
Jeremy Madeiros | " The management and protection of the small nesting islands where the endangered Cahow nests also has an added bonus, in that this also protects a number of other native and endemic plant and animal species. One of the most significant of these is the critically endangered Bermuda Skink, which used to be common across most of Bermuda, but is now found only on isolated offshore islands and in a few small, fragmented populations in coastal locations such as Spittal Pond. It is now one of the rarest lizard species on Earth, and is found on at least 4 of the small islands where the Cahow nests.
For many years, I have observed Skinks in Cahow nest burrows on these islands, often when the Cahows themselves are in residence. They seem to tolerate each other's presence, and there is evidence that the both species benefit from the association, with the Skinks using the burrows for shelter, eating insects, spilled food, infertile eggs etc., keeping the burrows clean and disease-free for the Cahows. It was known that a small colony of Skinks lived in the Cahow colony on Nonsuch, with surveys indicating that this population may have increased in the last couple of years; this was the first time that we had been able to record a skink visiting the CahowCam nest."
Mark Outerbridge | MSc, PhD, Wildlife Ecologist, Government of Bermuda
History
· The skink is Bermuda's only endemic, four-legged, terrestrial vertebrate (in other words they are the only living land animal with a backbone to have reached Bermuda before humans, and they exist nowhere else in the world)
· Skinks are descended from a species that once inhabited the eastern U.S.A. and subsequently dispersed over oceanic waters to Bermuda (Brandley et al., 2010)
· Fossil evidence indicates that skinks were living on Bermuda more than 400,000 years ago but paleontological and geological evidence suggest they may have been present here for 1-2 million years (Olsen et al., 2006)
· Skinks were historically described as being very common, frequenting the old walls and stone heaps in the cedar groves of Bermuda (Jones, 1859). Now, most of the fragmented populations are only found within the rocky coastal environment.
Ecology
· Adult skinks grow to 15-25 cm in length and weigh between 13-22 g. Hatchlings are 6 cm long, weigh about 1 g and have bright blue tails (which fades as they grow older).
· Skinks are thought to live for 20+ years
· Skinks are diurnal and are most active mid-morning and late afternoon
· Active year-round (they don’t brumate – reptile equivalent of hibernation - during the winter months)
· Ground dwelling species (don’t climbing trees)
· Omnivorous diet; insects, arthropods, prickly pear fruit and carrion from burrow-nesting birds (e.g. cahows and longtails)
· Oviparous species (i.e. egg laying). Nesting occurs in May and June (3-6 eggs typically laid on the soil under rocks). Females guard their eggs.
· Hatching begins in July and August after a 5 week incubation period.
Threats
· Bermuda’s skinks are now on the brink of extinction. They are listed as critically endangered and receive protection under the Protected Species Act.
· Habitat alteration and predation from introduced species are considered to be the main causes of population fragmentation and decline
· The total island-wide (hence global) population was estimated to be 2300-3500 individuals (Edgar et al., 2010)
· Skinks have been reported from at least 24 separate locations across Bermuda (Edgar et al., 2010) but the greatest concentration is found within the Castle Islands Nature Reserve
· Various population assessments have been undertaken over the past two decades. Some of the fragmented populations consist of only 50 individuals while others number in the hundreds. The largest population is currently found on Southampton Island (estimated 500 skinks).
Nonsuch skinks
· Surveys conducted on Nonsuch over the past 50 years suggest the population is declining and those skinks that remain are only found in a few locations on the island.
· In the early 1960s, the vegetation on Nonsuch was mostly grass and coastal shrubs – ideal habitat for skinks (dense ground cover for concealment from predatory birds and rich in insect prey)
· The reforestation efforts that have occurred since the 1960s drastically changed the interior of the island, making it less favorable as suitable skink habitat (Wingate, 1998)
· The creation of the two cahow nesting sites is expected to benefit the skinks; as the cahow colony grows on Nonsuch, so too should the skink colony.