Adult Male Density Influences Juvenile Microhabitat Use in a Territorial Lizard

Abstract

Habitat choice often has strong effects on performance and fitness. For many animals, optimal habitats differ across age or size classes, and individuals shift habitat use through ontogeny. Although many studies document ontogenetic habitat shifts for various taxa, most are observational and do not identify the causal factor of size‐specific habitat variation. Field observations of the brown anole lizard (Anolis sagrei) show that juveniles perch on shorter and thinner vegetation than adults. We hypothesized that this variation is due to adult males forcing smaller juveniles to less preferred habitat. To test this assertion, we manipulated adult male densities in mesh enclosures with artificial trees to examine the response of juvenile microhabitat choice. We found that adult male density had strong effects on juvenile perch height, perch width, and substrate use, suggesting that age‐class competition contributes to the observed ontogenetic differences in habitat choice. We also found that time of day significantly affected juvenile perch height and substrate use. In many cases, our results suggest that juveniles distance themselves from adults using different microhabitats from those used in our control ‘no‐adult’ treatment. However, these findings were often body size dependent and varied depending upon time of day. This study highlights the complexity of juvenile perching behavior and demonstrates the role of intraspecific interactions in shaping habitat use by juvenile animals.

Lizard species on three islands off the Mexican Pacific Coast: effects of insularity

“…This could lead adult insular lizards to be active for a longer period of time compared with the population on the mainland where more juveniles and hatchlings were observed as active. This longer period of activity of adult lizards could increase the intraspecific competition that often results in cannibalism, leading hatchlings and juveniles to change their habitat use to avoid competition (Cooper et al, 2015;Delaney & Warner, 2017;Donihue et al, 2016). Our detection of this could decrease during the surveys.…”

Huracán Jova: efecto de un fenómeno meteorológico severo sobre lagartijas insulares en el occidente de México

“…Los efectos positivos de Jova sobre las poblaciones de lagartijas insulares de nuestro estudio se deben muy probablemente a la intensidad intermedia del huracán, a diferencia de Floyd (categoría 4) que redujo la abundancia inmediata de artrópodos y de lagartijas tras el paso del huracán (Schöner y Spiller, 2006). El claro efecto negativo de Jova sobre la vegetación de ISA, conlleva una disminución de las perchas para las lagartijas arborícolas A. nebulosus y U. bicarinatus, es decir, más lagartijas por percha, lo que probablemente incrementó la competencia inter e intraespecífica por este recurso (Delaney y Warner, 2017;Zeng et al, 2014). Sin embargo, el incremento en la talla y peso de las lagartijas A. nebulosus podría sugerir suficiente viabilidad del recurso alimenticio o incluso, el incremento de dicho recurso como sugiere Reagan (1991) con los defoliadores.…”

Reexamining the storage effect: Why temporal variation in abiotic factors seems unlikely to cause coexistence

“…Additionally, there is high temporal variation in recruitment (Dunham, 1980; Smith, 1981; Tinkle et al, 1993)—if combined with between‐species differences in recruitment, it would produce temporal niche partitioning. Finally, ontogenetic shifts in microhabitat suggest that competition may be concentrated within cohorts (Delaney & Warner, 2017). If competition is occurring within cohorts, it suggests that a year of high fecundity or initial offspring survival would cause high competition among juveniles—likely producing a covariance between environment and density‐dependence.…”