Parturient behaviour of a viviparous skink: evidence for maternal cannibalism when basking opportunity is low

We documented the behaviour of pregnant McCann’s skinks (Oligosoma maccanni) before, during and after parturition. Females were maintained in captivity from early pregnancy under thermal environments differing in basking opportunity (low, mid and high regimes). Thermal regime during pregnancy had little influence on maternal behaviours, including basking behaviour prior to birth and the duration of, and site selection for, labour. The majority of births (78%) occurred in the open and warm areas. Most females (61%; n?=?102 births, n?=?36 females) aided offspring post-birth by biting them free of the enclosing extra-embryonic membrane. Some females from the low regime consumed non-viable offspring, but whether this is a consistent difference among females held under different basking regimes requires further study. Many females (c. 79%) also exhibited a brief transient decrease in control of hind-limbs post-birth. Further studies on other squamates are recommended to shed light on the evolutionary history and possible conservation consequences of maternal behaviour during parturition.     

Attempting to Manage Complex Predator-Prey Interactions Fails to Avert Imminent Extinction of a Threatened New Zealand Skink Population

Abstract: The current primary threats to biodiversity on a global scale are species invasions and habitat modification. Management of vulnerable populations often involves a lengthy sequence of 1) research to identify threats and recommend management strategies, 2) active management, and 3) results monitoring to assess effectiveness of management. The last mainland population of the large, endemic New Zealand skink (Whitaker's skink [Cyclodina whitakeri]) provides an opportunity to test this process in a system where the synergistic effects between invasive species (introduced rodents and grasses) have predicted outcomes. A low abundance of Whitaker's skink at the Pukerua Bay Scientific Reserve in the 1980s prompted management recommendations to remove grazing stock and revegetate the site to simultaneously restore habitat and provide protection against introduced mammalian predators. Since Whitaker's skink have low detectability, it was recommended that sympatric copper skink (C. aenea) be used an indicator species of management effectiveness. Grazing stock were removed in 1987, but efforts to revegetate the site were ineffective. Long-term monitoring (1984-2006) of the Whitaker's skink population and 4 other sympatric lizard species within a 336-m² area at the site resulted in 1,693 lizard captures over 7,597 trap days. Whitaker's skink represented 2.8% of all captures in 1984-1988, but declined relative to other species to represent only 0.2% of captures in 2000-2006 (representing 2 individuals). Congeneric copper skink showed a similar decline with capture rates also approaching zero by 2006. Removing grazing stock did not result in an increased abundance of Whitaker's skink or copper skink through improved habitat quality, as was intended by the management recommendation. Instead, reduced grazing has allowed introduced seeding grasses to proliferate, which may have led to periodic rodent irruptions, supporting a guild of introduced mammalian predators and depleting populations of Whitaker's skink and copper skink. In this instance, attempted protection may have driven a vulnerable population towards extinction. We recommend investigating the feasibility of constructing a mammal-proof fence around the core Whitaker's skink habitat, as the last remaining management option to salvage the population.     

Inbreeding and promiscuity in the endangered grand skink

The inbreeding avoidance hypothesis predicts that organisms that often encounter relatives as potential mates should evolve behaviours to avoid incestuous matings. Avoidance behaviours have practical importance for small populations because deleterious genetic processes may be less imminent than otherwise expected from genetic models that assume random mating. I used genetic techniques to investigate the extent of inbreeding and inbreeding avoidance behaviours in rare lizards from southern New Zealand. Grand skinks, Oligosoma grande, live in small patchily distributed groups, and have low rates of inter-group dispersal (ca. 3–20% disperse). I used data from 15 microsatellite loci to test the hypothesis that adults are likely to encounter kin as potential mates and will inbreed. These data showed that adult skinks usually inhabited rock outcrops with adult relatives of the opposite sex – up to 35% of potential mates were of equivalent relatedness as half-sibs and 17% were equivalent to full sibs. However, skinks did not preferentially breed with less related mates, and 18.2% of matings were between individuals of equivalent relatedness as full-sibs. Instead, skinks mated with partners of all levels of relatedness, and were promiscuous – almost half of adult females and nearly three quarters of adult males reproduced with multiple partners. In addition, inbreeding had no effect on survival of offspring in their first year. Two other putative mechanisms of inbreeding avoidance, sex-biased and natal dispersal, were not pronounced in this species. This study adds to a growing list of species that inbreed despite the risks.     

A significant range extension and sanctuary for the rare Open Bay Island skink (Oligosoma taumakae)

Abstract

The Open Bay Island skink (Oligosoma taumakae) is one of New Zealand's rarest lizard species. Until 2010, it was known only from two small islands in the Open Bay Island Group, a Māori-owned wildlife sanctuary in South Westland, New Zealand. Skinks on these islands are threatened by predation from weka (Gallirallus australis), a flightless native rail thought to have been introduced to the Open Bay Islands c. 100 years ago. Here, we describe the discovery of Open Bay Island skinks on two vegetated rock stacks located off the coast of Barn Bay, 52 km southwest of the Open Bay Islands. Although small (c. 0.10 and 0.36 ha), the Barn Islands appear to be predator-free, providing an important sanctuary for the skinks. We recommend: (1) a survey of mainland sites with suitable habitat; and (2) an evaluation of the need for island biosecurity measures for detecting and responding to incursions of small mammals.     

Pest fencing or pest trapping: A bio‐economic analysis of cost‐effectiveness

Scofield et al. discredited the utility of pest‐exclusion fences for restoring biodiversity partly on the grounds of unquantified costs and benefits. We estimated the discounted costs of mammal exclusion fences, semi‐permeable (‘leaky’) fences and trapping, over 50 years and adjusted costs by their observed effectiveness at reducing mammalian predator abundance. We modelled data from two large predator management programmes operated by the New Zealand Department of Conservation. Using typical baseline costs and predator control efficacies (scale 0 to 1), the model predicted that an exclusion fence (efficacy 1.0) is the cheapest and most cost‐effective option for areas below about 1 ha, a leaky fence (efficacy 0.9) is most cost‐effective for 1–219 ha, and trapping (efficacy 0.6, based on 0.2 traps per hectare and a 1500‐m buffer to reduce predator reinvasion) for areas above 219 ha. This ranking was insensitive to adjustments in efficacy, but reducing efficacy of leaky fences to 0.8 or increasing trapping efficacy to 0.7 reduced the cost‐effective range of leaky fences by about 90 ha. Reducing trap maintenance costs from $300 to $100 per trap per year (e.g. using long‐life lures), or reducing trap buffer widths to 500 m, significantly elevated trapping as the most cost‐effective method for areas greater than 11–15 ha. These results were largely consistent with an ecological measure of effectiveness based on observed rates of recovery of two indigenous skink species inside exclusion fences or with trapping. The results support criticisms that exclusion fences are generally not cost‐effective, but highlight the value of considering cheaper leaky designs for small‐ to medium‐sized areas. Because this study is based largely on reductions in predator abundance, it has general application to broader biodiversity protection interests, but not to indigenous species that are highly sensitive to predation and only ever adequately protected on the mainland by exclusion fences.     

Exploring the consequences of climate‐induced changes in cloud cover on offspring of a cool‐temperate viviparous lizard

Historically, studies on the response of ectotherms to anthropogenic climate change have emphasized predicted changes in temperature, with few examining responses associated with additional climatic changes. Basking behaviour is an absolute requirement for lizards from temperate regions because elevated body temperatures are needed for processes such as digestion and embryogenesis. Given that predicted cloud‐cover changes will alter basking opportunities in many locations, we measured the phenotypic consequences of an increase or reduction in basking opportunity during pregnancy on the offspring of a viviparous temperate skink. The sex, size, growth, survival, emergence behaviour, morphotype, pigmentation, and locomotor performance of offspring were measured up to 3 months of age. Most offspring characteristics (e.g. sex) were not influenced by maternal basking regime. However, maternal pregnancy success was lower, and female offspring were slower growing, and thus smaller, when from regimes mimicking high cloud cover, suggesting potential long‐term influences on population dynamics. Although a link between basking regime and phenotype has been reported in viviparous lizards, this is the first study to explore possible negative implications of changes in cloud cover on offspring production and phenotype (other than sex). © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 844–851.