Each season reveals a new chapter in the multiple micro-habitats that our biodiversity-monitoring project surveys (see post, Biodiversity Monitoring at Safari Park Reserve). The warm, dry weather means that we have been up before dawn every day this season, and it affects which critters might be active at this time of year as well. This summer we have seen fewer mammals in our arrays at the San Diego Zoo Safari Park Reserve in Escondido as compared to last spring, whereas the number of herptofauna findings has increased. However, due to the dry weather we have rarely seen frogs, which may be aestivating during these hot months. This last week was quite foggy and a bit cooler, so our September data includes a few common mammals such as gray shrews, California pocket mice, San Diego pocket mice, cactus mice, harvest mice, deer mice, and California voles.
After a few months of seeing big, gravid female lizards, we started find hatchlings in our pitfall traps! June marked our first sightings of side-blotch lizard, western fence lizard, and western skink hatchlings. In July, we started finding Gilbert’s skink hatchlings as well. By August, beautiful orange-throated whiptail hatchlings emerged! This month brought the first occurrence of granite spiny lizard hatchlings and a few juvenile striped racers (aka California whipsnakes).
Both orange-throated whiptail hatchlings and western skinks have bright blue tails and dark body-length stripes. Often my volunteers ask how I tell them apart! While they may be similar in size, they look quite different in detail. The western skink’s head is more rounded, and its scales are very smooth and shiny. In addition, the two species of endemic skinks are also easy to tell apart as hatchlings. Juvenile Gilbert’s skinks typically have bright pink tails, and western skinks have bright blue tails. Furthermore, the body-length stripes on the Gilbert’s skinks do not go past their hind legs, as do stripes on western skinks in juvenile form. Later in life, western skink adults have stripes down their sides, whereas Gilbert’s are darker in coloration and have no stripes at all, which makes them quite distinguishable.
Our local subspecies of western skink, the Coronado skink, is a California species of concern due to habitat loss. Orange-throated whiptails, western skinks, and Gilbert’s skinks all have brightly colored tails as juveniles as a defense adaptation that can be dropped if caught by a predator. The tail even continues to wiggle and move after it is cast off, which may allow the animal to potentially escape. All three species do not retain this tail coloration in their adult form, and it does not appear to be associated with a form of mimicry in these species. Furthermore, its tail grows back after being discarded. From the number of tailless hatchlings I have seen, it seems like this strategy is successful in aiding them to survive until they can learn from experience how to avoid predators.
Christine Slocomb is a research technician at the San Diego Zoo Institute for Conservation Research.