Marieke Lettink

Relative use of three types of artificial retreats by terrestrial lizards in grazed coastal shrubland, New Zealand

Artificial retreats are increasingly used to sample animal populations and in attempts to boost animal numbers in degraded habitats. Understanding how animals use artificial retreats and which designs are most effective is therefore important. We tested the influence of retreat type, time-of-year and site on the use of artificial retreats by three species of terrestrial lizards (McCanns skink Oligosoma maccanni, common skink O. nigriplantare polychroma, and common gecko Hoplodactylus maculatus) in a remnant of grazed coastal shrubland at Birdlings Flat, New Zealand. Monthly capture sessions took place at two sites between December 2003 and November 2004. During 2160 retreat checks, 898 captures of 388 individual lizards were made. Geckos dominated the sample and displayed strong preferences for artificial retreats made of Onduline over corrugated iron and concrete tiles. Skinks used all types of artificial retreats without apparent preference. For all species, use of artificial retreats varied with time-of-year and was lowest in winter months. We also operated pitfall traps at these sites and made 329 captures of 205 individuals during 1920 trap-checks. Pitfall traps produced samples dominated by skinks. We conclude that Onduline retreats are a promising method for detecting terrestrial species of gecko in open habitats. Long-term studies are required to quantify the benefits of providing artificial retreats in restoration projects.

Use of artificial cover objects for detecting red katipo, Latrodectus katipo Powell (Araneae: Theridiidae)

Introduction Katipo are endemic widow spiders belonging to the genus Latrodectus (Theridiidae), a genus notorious for the dangerous bites of adult females. Latrodectus has a global distribution and is represented in New Zealand by two species; L. atritus Urquhart 1890 and L. katipo Powell 1871. Recently, it was recommended that these be referred to as ‘black’ and ‘red’ katipo, respectively (Patrick 2002). Both species of katipo have declined throughout their respective coastal duneland habitats and ranges. A recent nationwide survey for red katipo revealed they were present at only 46% of sites where they had been recorded previously (Patrick 2002). Threats to red katipo are degradation and loss of habitat due to historical and on-going processes, including replacement of the native sand-binder pingao (Desmoschoenus spiralis) with introduced marram grass (Ammophila arenaria), deliberate and accidental spread of exotic species such as Monterey pine (Pinus radiata), and damage caused by stock and recreational vehicles (Griffiths 2001). Although red katipo appear to have declined in number and distribution, the scarcity of detailed historical records and lack of a nationallyimplemented standard survey methodology mean that current rates of population declines and range reductions are difficult to determine. Monitoring is sporadic and consists of repeated sampling of some known populations over time in combination with surveys at sites were red katipo are scarce and/or have been recorded previously. Such surveys rely on hand-searching of suitable habitat, ideally by experienced observers. The probability of detecting katipo may vary according to the complexity and structure of the habitat being searched (Patrick 2002), observer experience, time-of-year, and the developmental stage, with spiderlings and males being more difficult to detect than adult females (Troup 2004). This variability can remain despite efforts to standardise survey conditions in-so-far as this is possible. For instance, two successive 30 min searches conducted by experienced observers at the exact same site yielded 33 and seven red katipo, respectively (Patrick 2002). Collectively, these difficulties highlight the need for practical and robust monitoring methods. New Zealand Entomologist 29: 99-102 (2006)

Mating system and genetic variation in the endangered New Zealand takahe

The takahe (Porphyrio hochstetteri) is ahighly endangered flightless rail that isendemic to New Zealand. Only one remnantpopulation of takahe (∼120 adults) is left inthe wild in Fiordland, which has been thesource for introductions to four predator-freeislands. The objective of the present studywas to determine the mating system andamount of genetic variation in takahe usingmultilocus DNA profiling, in order to assist inthe management of the island populations. There was no evidence of extra-pair paternityfor the 27 (73%, n = 37) offspring towhich paternity could be resolved. Thepaternity of the remaining 10 offspring couldnot be resolved due to low levels ofminisatellite DNA variation, but in none wasthe resident male excluded. Overall, the DNAresults along with behavioral and life historyinformation indicate that extra-pairfertilizations should be rare or absent, andtakahe join a small but growing list oflong-lived species of birds that have beenshown to exhibit genetic monogamy. Inaddition, the levels of minisatellite DNAvariation detected in takahe are low relativeto those reported for most other known outbredavian populations, and are consistent with theevidence of the takahes persistence as asmall, isolated population in Fiordland over atleast the last 100 years. The low geneticvariation is discussed in relation to possibleevidence of environment depended inbreedingdepression in translocated island populationsof takahe.

Thermal properties of artificial refuges and their implications for retreat-site selection in lizards

Artificial retreats or refuges (ARs) provide a useful method for sampling lizards and a possible means of restoring habitat to aid population persistence. Previous research suggests that preferences for ARs may vary among species and between different designs. To test these ideas further, we examined the influence of thermal and structural characteristics on use of three types of ARs by the nocturnal common gecko (Hoplodactylus maculatus) and diurnal McCanns skink (Oligosoma maccanni), two lizards endemic to New Zealand. The field study confirmed that the three ARs (triple-layered Onduline, triple-layered iron, solid concrete) differed in retreat-site temperatures provided during each of three seasons (winter, spring and summer). In their top spaces, Onduline ARs were the warmest by day, coolest by night, and thus displayed the largest diel variations in temperature. In the laboratory, common geckos showed a significant preference for Onduline whether ARs were exposed to a radiant overhead heat source or not, whereas skinks did not display any preference among the three types of ARs regardless of heating. The three types of ARs provided field temperatures within the thermal preference range of both species (data obtained from the literature) but only for the top spaces of the ARs and only during summer. Onduline was the only AR to consistently provide the temperatures preferred by pregnant females. Although this study suggests that structural properties alone may be sufficient to explain the preference of geckos for triple-layered Onduline stacks, it does not eliminate the possibility that attractive thermal properties also contribute. Long-term studies are needed to test the effects of artificial refuge supplementation on reptiles, and on their predators and competitors.

Optimising the sampling of skinks using artificial retreats based on weather conditions and time of day

Artificial retreats are a low-cost, low-impact and effective technique for detecting cryptic taxa, such as herpetofauna, and have potential as a monitoring tool. The success of using artificial retreats for monitoring is dependent on our ability to maximise detection and minimise variability in sightings within a sampling period. Because ectotherms use retreats for their thermal properties, it may be possible to identify weather conditions during which animals consistently use retreats and design a monitoring protocol based on optimal conditions. We investigated the use of artificial retreats by common skinks, Oligosoma polychroma, in mixed grassland habitat in southern New Zealand under various weather conditions and at a range of times of day. We recorded 1175 sightings of skinks during 1800 artificial retreat checks over a nine day period in early summer 2008. Ambient temperature, rainfall, humidity and time of day were the strongest predictors of skink sightings beneath retreats. Skink sightings were highest and least variable: (1) in an ambient temperature range of 12-18°C, (2) during light or no rain, and (3) at low levels of relative humidity. Under optimal weather conditions, skink counts were similar during the day (8 a.m. to 5 p.m. inclusive) but lower during the evening (8 p.m.). Observer variability, type of substrate beneath the retreat and retreat colour did not significantly influence the number of skinks sighted. We highlight the need to optimise protocols for checking artificial retreats on a species- and site-specific basis before attempting to evaluate their use as a monitoring tool for herpetofauna.

Influence of Microhabitat Factors on Capture Rates of Lizards in a Coastal New Zealand Environment

Abstract The influence of trap placement on capture rate is poorly documented in herpetological studies and requires consideration, because optimizing trap sets can increase detectability of target species and improve capture rates generally. We conducted pitfall trapping for four species of terrestrial lizard in duneland, shrubland and farmland on Kaitorete Spit (South Island, New Zealand). Over 4,800 trap-days, 536 captures of 401 lizards were made. Five microhabitat factors were measured and tested for their ability to influence capture rates of Oligosoma maccanni and Oligosoma nigriplantare polychroma. Generalized linear mixed models revealed that the strongest overall influence on capture rate was the distance separating pitfall traps from the nearest cover (the greater the distance, the lower the capture rate). Weaker, positive influences on capture rate included the amount of vegetation cover surrounding traps and the presence of divaricating shrub and vine species, with some correlations between variables. Capture rates of O. maccanni and O. n. polychroma were highest in duneland and farmland, respectively. Our results show that simple measures such as placing pitfall traps close to cover, will improve capture rates for at least some species of New Zealand endemic skinks. Where such relationships are known in advance, trap placement may be deliberately manipulated to increase capture rates and standardized between sites to improve the validity of using capture rates as indices of relative density. Further research is needed to assess the effect of trap placement for other species and in relation to other factors that influence capture rates.