Relationships between head size, bite force, prey handling efficiency and diet in two sympatric lacertid lizards

Abstract

Summary 1.Relationships between morphology, bite force capacity, prey handling efficiency and trophic niche were explored in two sympatric species of lacertid lizards, Podarcis melisellensis (Braun 1877) and Lacerta oxycephala Duméril & Bibron 1839. 2. Head shape showed little variation, but head size (absolute and relative to snoutvent length, SVL) differed between species and sexes. Males have larger heads than females, both absolute and relative to their SVL. In absolute terms, male P. melisellensis have larger heads than male L. oxycephala , but the reverse case was true for the females. Relative to SVL, L. oxycephala have larger heads than P. melisellensis . 3. Bite force capacity was estimated by having the lizards bite on two metal plates, connected to a piezoelectric force transducer. Differences in maximal bite force between species and sexes paralleled differences in absolute head size. Differences in body size and head size explain the higher bite force of males (compared with females), but not the higher bite force of P. melisellensis (compared with L. oxycephala ). Among individual lizards, bite force correlated with body size and head size. 4. Prey handling efficiency, estimated by the time and number of bites needed to subdue a cricket in experimental conditions, also showed intersexual and interspecific variation. This variation corresponded to the differences in maximal bite capacity, suggesting that bite force is a determining factor in prey handling. Among individual lizards, both estimates of handling efficiency correlated with maximal bite force capacity. 5. Faecal pellet analyses suggested that in field conditions, males of both sexes select larger and harder prey than females. There was no difference between the species. The proportion of hard-bodied and large-sized prey items found in a lizard's faeces correlated positively with its bite force capacity. 6. It is concluded that differences in head and body size, through their effect on bite force capacity, may affect prey selection, either directly, or via handling efficiency.

Bite‐force performance of the last rhynchocephalian (Lepidosauria:Sphenodon)

“…A disproportionate increase in bite force during ontogeny in Sphenodon would permit adults to access relatively larger and harder prey than juveniles (Jones 2008), as well as a reduction in prey handling time as found in lizards (Capel-Williams & Pratten 1978;Herrel et al 2001a;Verwaijen et al 2002). In fact, differences in diet between juvenile and adult Sphenodon include a tendency for the former to feed on smaller prey items (Ussher 1999).…”

“…In lizards, bite force is related to feeding biology (e.g., Herrel etal. 1999;Lappin 1999;Herrel et al 2001a;Verwaijen et al 2002), and significant positive relationships have been identified between bite-force performance and male territoriality, combat, dominance (Lailvaux et al 2004;Lappin & Husak 2005;Husak et al 2006), and reproductive success (Lappm & Husak 2005;Husak et al 2009). …”

From set menu toa la carte. Linking issues in trophic ecology of Mediterranean lacertids

“…Contribution of hard prey .such as Coleoptera tends to increase with snout vent length (SVL) in lacertids at species level (Araujo, 1990, M.D. dissertation, University of Lisbon; Carretero & Llorente, 199D and species of similar SVL but different head size differed in their consumption of hard prey (Herrel et al, 2001;Verwaijen et al, 2002). However, there is no clear direct relationship between prey and predator sizes across species.…”

Sex size and shape differences in the lacertid community (Podarcisspp. andArchaeolacertasp.) from the Lake Skadar region (Montenegro)

“…The values of SSD indices based on head length (HL male estimated / HL female observed ) were 1.057 for P. melisellensis, 1.047 for P. muralis, and 1.025 for A. oxycephala. It is of interest to point out that we found greater SSD indices than in the previously analysed populations of P. muralis (Brãna 1996) and P. melisellensis and A. oxycephala (Herrel et al 2001a;Verwaijen et al 2002). The levels of overall dimorphism (calculated as Mahalanobi's distance based on all morphometric data) were D 2 525.064, for P. melisellensis; D 2 519.185 for P. muralis and D 2 521.040 for A. oxycephala.…”

“…The body size (decreasing order: P. muralis, P. melisellensis, A. oxycephala) and SSD (decreasing order: P. melisellensis, P. muralis and A. oxycephala) of the analysed lacertid species did not match completely, although the smallest species (A. oxycephala) had the lowest extent of sexual size dimorphism. It is noteworthy that Verwaijen et al (2002) also found that sexual dimorphism in head size was much less pronounced in A. oxycephala than in P. melisellensis.…”