The scale of reptile migration varies dramatically. Most oviparous lizards lay their eggs within their normal home ranges but many make directional movements to specialized breeding sites (Pough et al. 1998).
The famous Snake Road in Illinois’ Shawnee National Forest is closed every spring and fall as snakes and other reptiles migrate to and from LaRue Swamp. Aquatic snakes, such as Arafura filenakes, also show dramatic seasonal shifts in habitat utilization, moving from restricted ponds to floodplain grasslands at the onset of the wet season.
There are three major strategies for reptiles and mammals to survive cold temperatures: migration, hibernation or brumation. The National Park Service defines hibernation as a state of long-term inactivity, with an animal’s bod 게코도마뱀 y temperature and metabolic rate dropping, heart rate slowing down and breathing decreasing or stopping entirely. Hibernators can lose one-quarter of their weight, making them very vulnerable to predation and dehydration.
Many hibernating species such as ground squirrels, marmots and arctic hares require substantial food reserves to maintain their low metabolism. They may increase their food intake, scavenging for food and shelter in winter or collecting stored fat deposits from previous years to weather the lean times. They can also store a reservoir of fluids such as urine or blood, which they use to regulate their core temperature and keep water from escaping their body.
Climate change can influence the physiology of hibernators in a variety of ways, with impacts ranging from positive to negative. For example, warmer spring temperatures can cause hibernators to emerge from hibernation too early, when their fat reserves are critically low, and expose them to increased predation risk. In addition, warming winters can result in an accelerated onset of hibernation and reduced fat storage for some species, such as Daubenton’s bats (Myotis daubentonii) and Alpine marmots (Ursus ibericus). 게코도마뱀
The first signs of spring migration begin with waterfowl, as ducks, geese and swans start to move north once the frozen lakes and marshes thaw. Other birds, such as killdeer and red-winged blackbirds, also begin to migrate during early spring as do reptiles such as garter snakes (Tennessee) and rattlesnakes (Crotalis tigris). The latter show fidelity to both their dens and summer feeding areas by migrating back to the same sites each year. Similar fidelity is also shown by the aquatic species, the sea snake Pelamis platurus.
These and other herpetofauna show a great deal of flexibility in the timing of their seasonal movements. However, attempts to attribute this flexibility to climate change have been challenging due to the difficulty of identifying the appropriate location, time, scale and type of possible weather influences on migratory phenology. In addition, the inherent spatiotemporal autocorrelation and intercorrelation of weather variables can greatly increase the likelihood of false positives.
For example, the Snake Road, a paved highway that separates the Pine Hills of the Ozark Uplift from LaRue Swamp of the Coastal Plain, is closed for three weeks in the spring and fall to allow the snakes to move across it. In addition to being a vital wildlife passageway, the road provides herpetologists with unique opportunities to study their annual movements and behavioral changes.
The short breeding season in northern climates creates a high demand for food as days grow shorter. Waterbirds and shorebirds leave their Arctic breeding grounds for warmer waters where food is abundant. Birds such as whimbrels migrate the furthest, to sub-Saharan Africa. Their migratory timings reflect the relationship between food availability and the capacity to advance nest-laying dates.
Some birds migrate both north and south, or east and west. This type of migration is called altitudinal and involves moving up or down a mountain range. In the summer, skylarks and meadow pipits move up to high-altitude breeding habitat, while in winter they migrate down to lowland areas for food and milder temperatures.
As the seasons change, the pituitary gland signals the body to prepare for migration by accelerating gonad development and other metabolic processes. These changes can also be triggered by the amount of sunlight that is available, as well as by temperature and food availability.
Reptiles that live in wetlands face the additional challenges of altered hydroperiods and habitat fragmentation caused by climate change. Corridors linking upland foraging, overwintering and basking habitats may need to be created, as well as those preserving the integrity of aquatic breeding habitats. Non-native vegetation control and riparian buffer management are important considerations to retain open habitats with sufficient sun exposure.
Billions of birds annually migrate between breeding and nonbreeding grounds. This is a massive event that can span several months, depending on species. Peak Fall migration occurs between late August and October in New York City. Topographical cues such as coastlines, rivers, and mountain ranges guide birds along their route. Astronomical signposts like the sun and stars, as well as Earth’s magnetic field are also important.
After a pause for nesting and rearing young, Neotropical landbirds like warblers, tanagers, flycatchers, orioles, and jays begin their journey to tropical forests. These are insect-eating birds, and they leave before insects become scarce. They are nocturnal migrants that use complex star navigation, so we rarely see them during the day. They feed before they head out for the night, then rest and hide during daylight hours in order to remain hidden from predators.
By mid-October there’s a shift to temperate migrants, who are fruit and seed eaters. We see them in the mornings and evenings, often in straggling flocks. They’re not nocturnal, so we sometimes spot them during the day, particularly at locations where they roost.
Waterfowl and gulls follow, moving in response to weather conditions and food availability rather than a yearly clock. Birders look forward to the big flights associated with fronts and low pressure centers, which can produce what are known as ‘bird fall-outs’ when thousands of migrants concentrate in a small area. Stocking feeders with high-protein, no-waste wild bird mix such as Lyric Delite will help migrating birds bulk up and gain enough energy to complete their journey.