Aggregation behaviour of lizards in the arid western regions of South Africa

Abstract

Investigations of aggregation behaviour in five lizard species (three diurnal rockdwelling species, one nocturnal rock-dwelling species, and one diurnal terrestrial species) occurring in the arid western regions of South Africa revealed that there is no single set of causal factors explaining this behaviour. Aggregating behaviour in Cordylus macropholis is simply the result of environmental constraints, namely a shortage of preferred shelter sites. Individuals of Ouroborus cataphractus aggregate to benefit from the early predator detection effect. In Platysaurus broadleyi and Chondrodactylus bibronii aggregation behaviour appears to be the result of environmental constraints as well as possible benefits from the dilution effect. At present there is no conclusive information on the reasons for aggregation in Namazonurus peersi. In the rock-dwelling species investigated, the extent of adaptation to counter the effects of intra-group competition appears to be correlated with the proportion of activity time spent at the communal shelter. The proportion of time spent at the shelter, in turn, appears to be determined by the morphology of the species and whether it is diurnal or nocturnal.

An evaluation of daily, seasonal and population-level variation in the thermal preference of a group-living lizard, Ouroborus cataphractus (Sauria: Cordylidae)

“…Thermal quality is a function of Tp, and the low Tp of O. cataphractus there fore minimizes thermoregulatory costs for the species during spring and late winter, a criti cal time for energy acquisition, and furthermore enables accurate thermoregulation (Hertz, Huey and Stevenson, 1993) within crevices during summer and autumn when vitellogenesis, sper matogenesis and gestation take place (Flem ming and Mouton, 2002). The permanent group-living behaviour of O. cataphractus constrains food availability at the individual level (Mouton, 2011;Shuttleworth, Mouton and Van Niekerk, 2013). In fact, seasonal analyses of both stomach con tents (Mouton, Geertsema and Visagie, 2000) and bone histology (Curtin, Mouton and Chinsamy, 2005) confirm periods of extreme food stress in the species (Mouton, 2011).…”

“…The permanent group-living behaviour of O. cataphractus constrains food availability at the individual level (Mouton, 2011;Shuttleworth, Mouton and Van Niekerk, 2013). In fact, seasonal analyses of both stomach con tents (Mouton, Geertsema and Visagie, 2000) and bone histology (Curtin, Mouton and Chinsamy, 2005) confirm periods of extreme food stress in the species (Mouton, 2011). The low Tp and associated increased thermal habitat quality of crevices during autumn, when food availability reaches an annual minimum, re laxes O. cataphractus'% energy budget, due to low thermoregulatory costs (Huey and Slatkin, 1976), and is likely a further characteristic of this species enabling permanent group-living in semi-arid regions.…”

Sharing refuges on arid islands: ecological and social influence on aggregation behaviour of wall geckos

“…Many animal species from a wide range of taxa permanently live within groups or form aggregations during certain phases of their life cycle, or under certain environmental conditions, due to beneficial effects (Mouton, 2011). The benefits and costs of living in groups vary from species to species, the latter generally including competition for food resources, reproductive interference and infanticide, inbreeding depression, and higher likelihood of transmission of diseases, parasites and of attracting potential predators with a stronger scent trail (Alexander, 1974; Gardner et al, 2015).…”

“…Chapple (2003) documented social aggregations in a group of Australian scincids and referred to enhanced vigilance against predators as one of the benefits of group membership. Mouton (2011) reviewed the tendency of five South African lizard species to aggregate in refuges and found that they mostly aggregate due to shortage of optimal shelters and/or for anti-predatory effects. This author argues aggregation behaviour to have resulted in strong male territoriality: adult males attempt to set up harems and only when aggregations become unmanageably big will more than one male occur in the same group (Mouton, 2011).…”

The past, present and future of African herpetology

“…In addition to habitat destruction, anthropogenic impact on African herpetofauna can be more direct in areas where reptiles and amphibians are used as food (Mohneke et al 2011). Lastly, some subject areas have been the subject of many studies which require synthesis to provide new insight and stimulus for new generations of herpetologists (Mouton 2011).…”