Parental care is a well-recognized phenomenon, often observed in mammals and birds that dedicate significant time and resources to their offspring. This leads many to wonder about parental involvement in other vertebrates, particularly reptiles like lizards. While most lizards do not extensively care for their young, notable exceptions reveal a more nuanced picture of reptilian parenting strategies.
Typical Parental Behavior in Lizards
Most lizard species follow a reproductive strategy where parental involvement ceases shortly after eggs are laid or young are born. This “lay-and-leave” approach involves females depositing eggs in a suitable location, such as buried in soil or under leaf litter, then departing. This behavior is linked to producing many offspring, with only a fraction expected to survive.
The young of most lizard species are precocial, meaning they are relatively self-sufficient and capable of fending for themselves almost immediately after hatching or birth. They possess the necessary instincts and physical capabilities to find food and avoid predators from a very early age. This strategy minimizes the energetic investment and risks for the parent, allowing them to focus on their own survival and future reproductive opportunities.
Lizard Species That Exhibit Parental Care
Certain lizard species and closely related reptiles demonstrate various forms of parental care. Some skink species, for example, guard their egg clutches. The five-lined skink (Plestiodon fasciatus) is a well-documented example, where the female curls around her eggs until hatching, occasionally leaving to feed. If disturbed, she may even return them to the nest cavity.
More extensive parental care is observed in species like the prehensile-tailed skink, whose live-born young remain with parents for six months to a year. Both parents actively defend young from predators, and offspring may ingest adult feces to acquire beneficial gut bacteria. Cunningham’s skinks (Egernia cunninghami) also aggressively defend their offspring from predators like snakes and magpies.
While not lizards, crocodilians, close reptilian relatives, offer intricate examples of parental care. Female crocodiles build elaborate nests, guard them fiercely, and respond to chirping hatchlings by uncovering the nest or gently carrying young to water. This protection can extend for months or up to two years, increasing hatchling survival. Some python species also exhibit parental care by coiling around their eggs, sometimes shivering to generate heat, maintaining stable temperature and humidity for incubation.
Factors Influencing Parental Care in Lizards
The rarity of parental care in lizards, compared to birds and mammals, is influenced by biological and ecological factors. Many lizards employ an r-selection reproductive strategy, prioritizing numerous offspring with minimal individual investment. This contrasts with K-selection, where fewer offspring receive greater parental investment.
Parental care incurs significant energetic costs, including guarding eggs or young, and lost opportunities for foraging or future mating. Staying with offspring also increases the parent’s predation risk, as their presence might attract predators. Evolution favors strategies maximizing lifetime reproductive output; thus, if care costs outweigh benefits of increased offspring survival, parental care is unlikely to evolve.
Environmental conditions also play a role. Parental care is more likely to evolve when nests are in exposed locations, parents can defend eggs from predators, and incubation periods are brief. However, if the environment is stable with safe nesting sites, or if offspring are robust, parental care benefits might not justify its costs. Diverse strategies across lizard species reflect adaptations to their ecological niches and trade-offs between parental survival and offspring success.