Do Geckos rest with their food?

A study of Tenerife gecko (Tarentola delalandii) refuge and their proximity to food sources

Ben Owen & Georgie Eccles

Optimal foraging theory & Geckos•Animals spend a considerable time foraging for essential food resources.

•Foraging strategies vary greatly within phyla but the objective of attaining valuable food resources applies to all. •Optimal foraging theory- animals behave in ways that maximize net energy gain or benefit/ cost ratio (Aowphol et al, 2006).

•Tenerife geckos, Tarentola delalandii are small, nocturnal lizards which are predators of small invertebrate species.

•During the day these geckos take refuge under rocks in which they rest.

Aims• To investigate whether an association between gecko daytime refuge and proximity to their food

sources was occurring at Poris de Abona.

• Does abundance of food sources influence gecko refuge choice?

• Do either of the above factors have an association with gecko body length (Snout-to-vent length)?

We predict:1. Invertebrate abundance will influence gecko rock choice.2. Snout-to-vent length (SVL) is influenced by the abundance of local food sources.

Field methodology• Looked for a rock with a gecko.

• Once a gecko was found a 1x1 metre quadrat was placed in front of the rock (focal rock).

• Data collected from the quadratInvertebrate species numberNumber of invertebrate individuals

• Snout-to-vent length of the gecko was recorded when possible.

• After data collection 20 paces was taken in a random direction away from the gecko.

• The closest suitably sized rock without a gecko was used for data collection and the quadrat measurements were repeated.

Area of investigation at Poris de Abona

Invertebrates

Stenidea albida Scantius aegyptus

(Bramwell & Bramwell 1987; Wheater & Read 1996)

Other species found includedSilverfish, Lepisma saccharinaBlack beetle, Hegeter grancanariensis

• Data was later input into IBM SPSS 21 for analysis

• After eyeballing the data we decided to reduce the influence of the outliers by using a log10 transformation on both the snout-to-vent length and invertebrate abundance variables.

• A binomial regression (Generalised Linear Model) was used to analyse the relationship between gecko presence and invertebrate abundance

• A linear regression was used to analyse the relationship between gecko snout-to-vent length and invertebrate abundance

Data analysis

Results

Results

Discussion

• From our data it appears that gecko presence is positively influenced by invertebrate abundance.

• What does this mean in relation to optimal foraging theory?

• Contrary to what we predicted, our analysis of snout-vent length against invertebrate abundance showed that larger geckos select rocks with a lower abundance of invertebrates.

• This could be due to disproportionate consumption of invertebrates by larger geckos.

• What were the limitations of our study?

• Further study of interest?

References• Aowphol, A.,Thirakhupt, K.,Nabhitabhata.J,& Voris, H.K.( 2006) Foraging ecology of the

Tokay gecko, Gekko gecko in a foraging area of Thailand. Amphibia-Reptilia, 27, 491-503

• Bramwell, D. & Bramwell, Z. (1987) Historia natural de las islas Canarias. Editorial Rueda. Madrid.

• Wheater, C.P. & Read, H.J. (1996) Naturalists’ Handbooks 22: Animals under logs and stones, Richmond, Slough

Any Questions?