The question of whether lizards migrate, as birds or fish do, requires understanding movement within the context of reptile biology. Lizards do not undertake the classic, long-distance, seasonal, round-trip journeys associated with true migration. Their movements are localized and driven by immediate physiological needs, primarily relating to temperature regulation and resource acquisition within a relatively small area. The scale and purpose of their travel differ significantly from animals known for cyclical migrations.
Defining True Migration
True animal migration is defined as the persistent, long-distance movement of a population from one habitat to another, typically on a cyclical or seasonal basis. This movement is usually a two-way journey that involves a return to the original area, often for breeding or to escape resource scarcity. Classic examples involve species traveling thousands of miles, such as the annual movement of wildebeest or the flights of many bird species.
The movements are generally synchronized across an entire population and are a programmed response to annual changes in climate or food availability. In contrast, the daily or seasonal movements of most lizards do not fit this definition because they lack the long-distance travel component. A lizard’s movement is rarely population-wide and is not a sustained journey over varied terrain with the intent to return from a distant location.
Standard Lizard Movement: Home Range and Dispersal
The majority of a lizard’s movement is confined to a home range, an area regularly used for all routine activities. Within this territory, movement is daily and non-seasonal, primarily focused on finding food, basking to regulate body temperature, and seeking mates. These ranges are small, with many species confining their routine travel to a limited area.
Studies on certain green lizard species indicate that adult males average daily movements around 59 meters, while females travel closer to 22 meters. The sizes of these home ranges are tied to an individual’s foraging strategy and body size. Lizards that actively search for prey require larger home ranges than “sit-and-wait” predators, who remain stationary and ambush food.
Another type of significant movement is dispersal, which is a permanent, one-way relocation, often undertaken by juvenile or sub-adult lizards. Dispersal is a movement away from the birth site to establish a new home range elsewhere, driven by factors like overcrowding or competition for resources. This movement is not cyclical, and the individual does not return to its original territory.
Distances covered during dispersal are short when compared to true migration, often spanning only tens of meters away from the natal area. Juvenile dispersal distances have been recorded between 16 and 24 meters in some common lizards. This is a single relocation event, serving to reduce competition and facilitate gene flow between local populations.
Seasonal Shifts for Shelter and Survival
While lizards do not migrate to warmer climates, they exhibit localized, seasonal movements related to survival in extreme temperatures. As ectotherms, their body temperature is regulated by the external environment, forcing them to seek shelter when conditions become too cold or too hot. These movements are short-distance shifts aimed at finding a stable microclimate.
During cold seasons, lizards in temperate zones find a safe, stable location, known as a hibernaculum, for a period of dormancy called brumation. This movement is typically only a few meters into a deep burrow, under a rock pile, or inside a rotting log where temperatures remain above freezing. Brumation is a metabolic slowdown that allows the lizard to survive a lack of food and cold temperatures until spring returns.
In extremely hot or dry conditions, some lizards will undertake a brief movement to enter aestivation, a period of summer dormancy. This involves finding shelter from drought and heat, often by burrowing underground where the humidity is higher and the temperature is cooler. The motivation for both brumation and aestivation is temperature regulation and survival, distinguishing these actions from true animal migration.