Investigating Kleptothermy: A Reptile-Seabird Association with Thermal Benefits

Abstract

Studies on interspecific interactions between vertebrates based on thermal benefits are poorly represented in the literature. Ecologists know little about a category of thermoregulation termed kleptothermy. We provide evidence that a close association between a medium-sized reptile (tuatara, Sphenodon punctatus) and a small seabird (fairy prion, Pachyptila turtur) enables the reptile to maintain higher-than-average body temperatures. This is the first multiyear data set to reveal that the presence of an endotherm within a burrow has direct, transferable thermal benefits to an ectotherm. It is possible that such positive interspecific interactions may alleviate thermal stress across the range of a single species. Currently, we know little about the evolutionary consequences of such interactions, and future work should focus on whether these thermal benefits increase fitness through increased growth rates or reproductive output.

Is the breeding behaviour of nesting seabirds influenced by the presence of a predatory reptile—the tuatara?

“…However, assessing this would require a longer-term study looking at rates of burrow turnover and mate fidelity with tuatara presence. In certain instances, it may be that this interaction is best classed as a parasitism with the tuatara benefitting from burrow use, an enhanced microclimate (Corkery et al 2014) and easy predation opportunities (Walls 1978;Markwell 1998) in certain cases (although none were documented in the present study) to the detriment of the lifetime reproductive success of the fairy prions. In other instances it may simply be a case of competition for a limited resource (a burrow) with the outcome varying depending on the individuals and the circumstances involved.…”

Contrasting responses of lizard occurrences to burrowing by a critically endangered seabird

“…We included the effects of potentially important covariates on both occupancy (Y) and detection probabilities (p) in our models. Specifically, we hypothesized that Y could be affected by the presence of Diving Petrel burrows (Walls 1978, Markwell and Daugherty 2002, Corkery et al 2014, the presence of the other skink species (Petren and Case 1998), the vegetation cover (Berry et al 2005, Seddon et al 2011, and/or the distance to sea (Fischer et al 2018c). Consequently, we modelled the influence of 1) the presence of a Diving Petrel burrow (binomial; denoted as burrow), 2) the presence of the other skink species (i.e., naïve occupancy; binomial; denoted as sgs or sigs for southern grass skinks and Stewart Island green skinks, respectively), 3) the vegetation cover (m 2 ; modelled as a quadratic function when a concave relationship was detected, or as a linear function when a convex relationship was detected; denoted as veg 2 or veg, respectively), and 4) the distance to sea (m from the spring-tide line; denoted as sea) on the of both skink species.…”

“…As an exception, the large and enigmatic tuatara (Sphenodon punctatus) has been shown to benefit from co-habiting fairy prion (Pachyptila turtur) burrows. Tuatara benefitted from warmer internal temperatures when inhabiting prion burrows and fed on prion chicks (Corkery et al 2014(Corkery et al , 2015. In addition, lizard communities (Scincidae and Diplodactylidae) were found to be more abundant and diverse on islands inhabited by seabirds than seabird-free islands (Markwell and Daugherty 2002).…”

“…Both are listed as listed as "At Risk -Declining" in New Zealand following considerable range reductions caused by predation by invasive predators and habitat destruction (Hitchmough et al 2016, Jewell 2017. Based on the studies conducted on tuatara (Corkery et al 2014(Corkery et al , 2015, we hypothesised that the two threatened small lizard species in the dune of Codfish Island would occur more frequently at sites with Whenua Hou Diving Petrel burrows than at sites without. To test our hypothesis, we used a large number of repeat surveys and occupancy modelling to account for imperfect detection of both skink species.…”

The first recorded interaction between two species separated for centuries suggests they were ecological competitors

“…However, tuatara frequently invade the burrows of another burrowing bird, the fairy prion/tītī wainui (Pachyptila turtur), on Stephens Island/Takapourewa rather than digging their own burrows. The tuatara seemingly benefit from the association via not having to spend energy digging a burrow and via kleptothermy (heat stealing) (Corkery et al 2014), but there is little advantage to this symbiosis for the prions. The two species compete for space when in single chamber burrows (Walls 1978), tuatara regularly prey upon prion eggs and chicks while sharing burrows (Newman 1987), and prions have been shown to enter burrows later and spend less time in them with their chick when tuatara are present (Corkery et al 2015).…”