Picking a tree: habitat use by the tree agama, Acanthocercus atricollis atricollis, in South Africa

We studied tree agama (Acanthocercus a. atricollis) habitat use in the Magaliesberg mountain range in northern South Africa using sightings of marked individuals, and in a few cases, radio-telemetry. Acanthocercus a. atricollis preferentially selected thorn trees (46%; Acacia karroo), followed by common sugarbush (10%; Protea caffra) and dead trees (9%). The type of tree selected was unrelated to lizard age class or sex. Multivariate analysis failed to show any age class or sex effects for specific tree physical characteristics, but did reveal a preference for trees with greater diameter, canopy cover and incidence of parasitic plants. We suggest that more ‘complex’ trees may enhance crypsis, facilitate escape from predation, or provide a foraging advantage. Acanthocercus a. atricollis selected night-time perches higher than those used during the day, possibly further offsetting predation risk.Keywords: tree selection, age-sex differences, nocturnal retreat sites, lizard, reptil

Data from: Building a beetle: how larval environment leads to adult performance in a horned beetle

The link between the expression of the signals used by male animals in contests with the traits which determine success in those contests is poorly understood. This is particularly true in holometabolous insects such as horned beetles where signal expression is determined during metamorphosis and is fixed during adulthood, whereas performance is influenced by post-eclosion feeding. We used path analysis to investigate the relationships between larval and adult nutrition, horn and body size and fitness-related traits such as strength and testes mass in the horned beetle Euoniticellus intermedius. In males weight gain post-eclosion had a central role in determining both testes mass and strength. Weight gain was unaffected by adult nutrition but was strongly correlated with by horn length, itself determined by larval resource availability, indicating strong indirect effects of larval nutrition on the adult beetle’s ability to assimilate food and grow tissues. Female strength was predicted by a simple path diagram where strength was determined by eclosion weight, itself determined by larval nutrition: weight gain post-eclosion was not a predictor of strength in this sex. Based on earlier findings we discuss the insulin-like signalling pathway as a possible mechanism by which larval nutrition could affect adult weight gain and thence traits such as strength

Temporal constraints and female preference for burrow width in the fiddler crab, Uca mjoebergi

Abstract We studied sampling behaviour and mate choice in the fiddler crab Uca mjoebergi. Once a female selects a mate, she copulates in his burrow and remains there until releasing her aquatic larvae. U. mjoebergi occurs in habitats that are inundated only by the highest amplitude spring tides. Females can only release their larvae during these tides, and release before or after will result in complete failure of reproductive effort. Matings occur over a 5-day period near the end of neap tides. Our results suggest that within the mating period, females adjust their larval developmental rates by selecting specific burrows in which to incubate their clutches. We found that at the start of the mating period, females chose larger males as mates. Since male size was positively correlated to burrow width, females were selecting wide burrows and effectively incubating at lower temperatures. This would slow down the developmental rates of larvae. In contrast, females that mated late in the mating period selectively chose small males. By incubating in narrower, warmer burrows, these females may increase the developmental rates of larvae. We propose that females are selecting burrows to influence incubation rate and ensure timely release of their larvae. Female U. mjoebergi appear to adjust their preference for the direct benefits of mate choice to increase their reproductive success

Female data

Data on weight, performance etc. for female beetles. See supplementary information for details of the analysis

Male data

Performance, weight etc. data for male beetles. See supplementary information for full details of the analysis

Path diagrams for the final models explaining the relationship between female (A) and male (B) maximum strength and larval nutrition, adult morphology and post-eclosion weight gain.

<p>Solid lines indicate positive relationships, dashed lines negative, double headed arrows indicate correlation (i.e. no assumptions about causality) and line width is proportional to the strength of the relationship. Numbers next to arrows indicate regression or correlation coefficients calculated from standardized predictor variables. Haemolymph protein content, overall fat content and adult diet treatment were not retained in either model and so are not shown.</p

Ecology of Wahlberg’s velvet gecko, Homopholis wahlbergii, in southern Africa

We examined 170 museum specimens of the southern African gekkonid lizard Homopholis wahlbergii, to quantify sexual dimorphism, male and female reproductive cycles and diet. The largest male and female we recorded were 116 and 119 mm snout–vent length (SVL) respectively. We compared SVL, tail length, head length, head width and eye diameter and found no evidence of sexual dimorphism in any of these characters. The smallest female with thickened muscular oviducts and follicles, indicating sexual maturity, was 59 mm SVL, but the smallest female we found with fully developed eggs was 85mmSVL. Virtually all females larger than 59 mm appeared to be in some stage of reproduction, suggesting that females  reproduce every year once they reach sexual maturity. Egg size ranged from 17–19mmlong. Egg size was not correlated with maternal SVL. We found adult females with ready-to-lay eggs during the warmer months of the year, but not during winter and spring. The smallest sexually mature male was 72 mm SVL. Virtually all males larger than this size displayed at least semi-turgid testes and most adult male testes were at least semi-turgid for much of the year. The only significantdecrease in testicular activity was in mid-winter (June–August), thus,  spermatogenesis is closely tied to female follicular development and ovulation. Velvet geckos are largely insectivorous (92%) and feed on a broad spectrum of prey. Their diet was dominated both numerically (34%) and volumetrically (22%) by beetles. Lepidoptera were the next most important prey category, suggesting that they exploit both terrestrial and flying invertebrates. They are unusual among lizards because they feed on millipedes. Males and females had very similar diets which may be explained by their lack of sexual dimorphism, although females tended toeat a greater volume of prey. Interestingly, less than half (37%) of the lizards examined contained prey items, suggesting that most individuals were not in positive energy balance.We also found evidence of prey size selection as a function of gape size, such that larger geckos took advantage of larger prey items.Key words: lizard, life history, sexual size dimorphism, diet, reproduction

Path diagrams for the final models explaining the relationship between female (A) and male (B) adult fat content, testes mass (males only) and larval nutrition, adult morphology and post-eclosion weight gain.

<p>Solid lines indicate positive relationships, dashed lines negative, double headed arrows indicate correlation (i.e. no assumptions about causality) and line width is proportional to the strength of the relationship. Numbers next to arrows indicate regression or correlation coefficients calculated from standardized predictor variables.</p