Reptiles move between habitats in response to seasonal changes and environmental conditions. These movements can also be influenced by climate-induced shifts in ecosystem boundaries and thermal attributes of landscapes.
After emerging from their dens or hibernacula, snakes disperse to summer habitats. Their directional migrations may be guided by visual cues such as topographical features or the pattern of polarized light in the sky.
A favorite of swimmers and snorkelers, sea turtles are renowned for their longevity and peaceful demeanor. They can be found in all of the world’s oceans except polar waters. Some species of sea turtle, including hawksbills, loggerheads and flatbacks, nest in New York’s beaches and Long Island Sound.
While many land-based animals can pinpoint their locations with relative ease, animals that migrate through the ocean have much less information to go on. How exactly sea turtles, fish and birds find their way has stumped scientists for decades.
A recent study of hawksbill turtles, one of the largest sea turtles with a worldwide distribution, may provide some clues. Researchers attached GPS tracking devices to 22 of the reptiles after they completed a nesting season on Diego Garcia, an island in the Chagos Archipelago. They then tracked the turtles’ journeys back to their foraging habitats in nearby waters. The maps that showed the turtles’ routes looked like the scribbles in a child’s coloring book, with many random loops and double-backs.
Despite their zig-zagging, the turtles were able to reach their intended destinations with impressive accuracy. The turtles could rely on visual landmarks to guide them, and they also used wind-borne cues that emanated from their target site to help navigate. Additionally, the turtles seemed to be able to perceive the Earth’s magnetic field.
In addition to being able to sense the Earth’s magnetic field, hawksbill sea turtles also seem to be able to see in very dark conditions. This ability is likely a result of the fact that they have more cells that detect dim light (rods) than cells that detect bright light (cones). This allows the reptiles to scour the deep ocean for jellyfish, their primary prey, which spend part of their day in the darker depths.
Snakes are elongated, limbless reptiles in the order Squamata (suborder Serpentes). Like all other squamates, they are ectothermic and can’t create their own body heat. To regulate their internal temperature they must obtain heat from the environment – they absorb it from the ground, the air or objects adjacent to them and can produce some heat by flexing their muscles. As a result, they are able to survive in habitats that would be hostile to warm-blooded birds and mammals.
They spend 70% of their solitary lives hunting, capturing and digesting living prey. Unlike lizards, snakes are carnivorous and consume a wide range of animal species including invertebrates, fish, amphibians, birds and their eggs, and mammals. Some snakes have ingenious systems for subduing and swallowing large or dangerous prey. Some have an expandable gape that enables them to gulp whole prey items much larger than their head, others have rear-fanged teeth that inject venom into the victim through grooves in the teeth.
In the wild, snakes are generally solitary but may congregate in favorable environmental conditions such as overwintering sites or nesting areas. They mate during the warmer months and lay their eggs in secluded places such as under rotting logs, rocks, in termite galleries, in holes in the ground or in other secluded spots. Egg laying takes place in early spring and the young hatch when weather conditions are suitable.
Snakes are constantly on the move seeking basking or shedding sites, food, water, mates, nesting areas or overwintering habitat. They are also influenced by their surrounding environment and can be triggered to take action to protect themselves from extreme conditions. For example, if the ground temperatures are too cold, they will hibernate, and if it is too hot they will seek shelter to avoid overheating.
The term “lizard” covers an amazing diversity of reptiles that include geckos, iguanas and worm lizards. They all belong to the order Squamata, along with snakes. They differ from mammals in that they lack a warm body core and instead rely on their skin for heat retention. The ability to move in a variety of ways enables them to survive in different climates. Geckoes, for example, can use their enlarged pads to climb up vertical surfaces and even overhanging ones. They can also drop their tails, which are held in place by weakened vertebrae, and they can regrow them, though not to the same length or look as the original one.
Most lizards are ectotherms, so they need to find warm places to raise their body temperatures to the optimum level for hunting and mating. They tend to be solitary, with males guarding their territory from rivals. Females lay soft, leathery eggs and rarely visit the nest to provide warmth.
When it comes to defending their territories, lizards often bob their heads as a way of looking bigger and more intimidating to prey and predators. They can also lick their tails to suck up food.
In some species, large males compete with each other for access to females, and the larger the lizard, the more likely it is that sexual selection will favour him. In other cases, the females are the dominant players and so size doesn’t play a role in mate preference.
For reptiles that live over a wide climatic range, judicious changes in nest depth and degree of shade can help ensure that their offspring experience similar conditions across their entire distribution. But the time-window of favourable thermal conditions may be getting smaller as global climate change impacts on both tropical and temperate zone species.