Deinacrida Research Articles

Mating assortment and the strength of sexual selection in a polyandrous population of Cook Strait giant weta

AbstractPolyandry can profoundly affect the strength of pre-copulatory sexual selection acting on males because each additional mate acquired by a female means that, all else being equal, a male’s paternity share declines. However, accruing additional mates could benefit male fitness if males with greater mating success also tend to have less promiscuous females as partners. If this is indeed the case, then males should experience strong sexual selection to acquire more mates. We tested these predictions by collecting detailed mating data on male and female Cook Strait giant weta (Deinacrida rugosa) in the wild via daily radio tracking. Our sexual network-based approach indeed revealed that the most polygynous male D. rugosa mated the least polyandrous females. This finding therefore suggests that the most successful males likely face lower intensities of sperm competition and so should be selected to accrue more mates. Further, our selection analysis revealed significant pre-copulatory sexual selection on males with those having relatively smaller body size, lighter body mass, and longer legs accruing more mates than otherwise. Thus, it appears that both pre- and post-copulatory episodes of sexual selection reinforce the same male phenotype.

From farm to forest – 50 years of ecological transformation on Mana Island, New Zealand

Ecological surveys of Mana Island, Wellington, in 1972 and 1975 confirmed that house mice (Mus musculus) were the only pest mammals present, and resulted in nationally significant populations of Cook Strait giant weta (Deinacrida rugosa) and of two threatened lizard species being confirmed or discovered. Photographs taken in June 1972 were re-taken in June 2022, and are used to document social and ecological change on the island over this 50-year interval. Mana Island was farmed until 1986, and has been a conservation reserve administered by the Department of Conservation (DOC) since 1987. Mice reached plague numbers after farm stock were removed, and caused a population crash of McGregor’s skink (Oligosoma macgregori). Following mouse eradication in 1989–90, the island has been free of introduced mammals. A major revegetation effort since 1987 included planting of more than 443,000 trees and shrubs over about 36% of the 217 ha island. For the last two decades, conservation management of the island has largely followed a comprehensive ecological restoration plan that was published in 1999. The Friends of Mana Island was formed in 1998, and has taken the lead role in most conservation initiatives on the island since then, in partnership with Ngāti Toa Rangatira (mana whenua) and DOC. In addition to the revegetation programme, weed control, and recreation of a wetland, 22 animal species have been translocated to the island, and several bird species have colonised naturally. Conservation successes and failures are described, and research relevant to restoration ecology undertaken on the island is summarised.

Effect of body condition on mobility and mating success in a wild population of the scramble polygynous Cook Strait giant weta

Effect of body condition on mobility and mating success in a wild population of the scramble polygynous Cook Strait giant weta

Substrate-Borne Vibration Mediates Intrasexual Agonism in the New Zealand Cook Strait Giant Weta (Deinacrida rugosa)

Substrate-borne vibrational communication is a common mode of information transfer in many invertebrate groups, with vibration serving as both primary and secondary signal channels in Orthopterans. The Cook Strait giant weta, Deinacrida rugosa (Orthoptera: Anostostomatidae), is an endangered New Zealand insect whose communication system has not been previously described. After field observations of intraspecific interactions in D. rugosa provided preliminary evidence for substrate-borne vibrational communication in the species, we sought to identify the following: vibrational signal structure, the mechanism of signal production, whether signal production is a sexually dimorphic trait, whether substrate-borne signals encode information regarding sender size, the primary social context in which vibration is utilized and finally, the function of vibrational signaling in the species. We used laser Doppler vibrometry to show that D. rugosa males produce low frequency (DF = 37.00 ± 1.63 Hz) substrate-borne vibrations through dorso-ventral tremulation. Rarely produced by females, male signals appear to target rivals while both are in the direct physical presence of a female. Tremulatory responses to playbacks were only produced by males in male-male-female trial contexts, and neither sex exhibited walking vibrotaxis to playback signals, indicating that substrate-borne vibrational signals are not likely a component of the courtship repertoire. While we found that vibrational signal structure was not closely related to signaler size, males that initiated male-male signaling bouts held a significant advantage in contests.

Saving the 'God of ugly things'.

Nearly wiped out by invasive mammals, New Zealand's mouse-sized insects, called giant weta, are making a comeback.

Do Male Cook Strait Giant Weta Prudently Allocate Sperm?

Sperm production is costly and so males are expected to prudently allocate sperm to matings in a manner that maximizes their fitness. Sperm competition hypotheses predict that when facing increased sperm competition risk males should increase their investment in ejaculates. In contrast, when facing high future mating opportunities, males are expected to decrease their sperm investment in the current mating. This is because males should keep in reserve an amount of sperm proportional to their expected future mating opportunities. We experimentally tested whether male Cook Strait giant weta (Anostostomatidae: Orthoptera: Deinacrida rugosa) phenotypically adjust their investment in ejaculates in relation to their perceived risk of sperm competition and future mating opportunities. D. rugosa is a large flightless orthopteran insect in which males pass multiple spermatophores to females during a day-long mating bout. Contrary to expectation, we found that low female availability (i.e. increased sperm competition risk) had no effect on male resource allocation to sperm (i.e. number of spermatophores) compared to controls whereas, contrary to expectation, males experiencing high female availability increased their ejaculate investment by transferring significantly more spermatophores to their mates. Our results might be a consequence of males being insensitive to increased presence of rival males, reducing their allocation to sperm under increasingly risky circumstances, or due to females prolonging copulations when their perceived future mating opportunities are low.

Population history and genetic bottlenecks in translocated Cook Strait giant weta, Deinacrida rugosa: recommendations for future conservation management

Translocating populations of endangered animals to predator-free offshore islands is an extreme, and potentially risky, conservation management strategy. There are many examples of failures and successes, however relatively little work has been done to formally quantify the required numbers of translocated individuals to increase the chance of successful establishment. Cook Strait giant weta, Deinacrida rugosa Buller 1870 (Orthoptera: Anostostomatidae), of New Zealand are an example of an at-risk species where extreme conservation measures are needed, due to their ground-dwelling lifestyle making them particularly prone to habitat loss and predation by alien species following human settlement. Here, we have used microsatellite markers to characterise genetic diversity within and between two parental populations (Mana and Stephens Islands), and two translocated populations (Maud and Matiu/Somes Islands), and estimate probabilities of genetic bottlenecks. We have modelled various demographic scenarios to quantify the severity of effective population size fluctuations resulting from translocations using DIYABC, and explored the number of founders needed to retain rare alleles using ALLELERETAIN. Our results suggest that populations have expanded on both Maud Island and Matiu/Somes Island from effective population sizes at time of translocation of 36 and 47 respectively, but provide evidence for a genetic bottleneck on Maud Island. We also show that translocations have had minimal impact on parental effective population sizes. The impact of our results on future conservation management efforts is discussed.

Effect of nutritional stress and sex on melanotic encapsulation rate in the sexually size dimorphic Cook Strait giant weta (Deinacrida rugosa)

Nutritional condition and sex are known to influence efficacy and investment in immune function. A poor diet is costly to immune function because it limits the resources (e.g., protein) available to effector systems (e.g., melanotic encapsulation), whereas males and females are expected to differ in how they allocate resources to fitness-related traits. Males are expected to invest less in immunity, and more in mating, than females, but this pattern could be reversed if fitness is more condition-dependent in males than in females. I tested the effects of nutritional condition and sex on melanotic encapsulation rate in the Cook Strait giant weta (Deinacrida rugosa Buller, 1871), an orthopteran insect exhibiting strong female-biased sexual size dimorphism that is, at least in part, the result of strong sexual selection for small male size. I found that male D. rugosa have a stronger encapsulation response than females, while nutritional condition has only a small positive effect on this particular effector system in both sexes. Whether the observed sex difference in encapsulation ability is due to a physiological constraint in females or whether males allocate more resources to this effector system because their fitness is more condition-dependent than female’s remains to be determined.

The effect of condition on mate searching speed and copulation frequency in the Cook Strait giant weta

Nutritional condition is important to the function and performance of several facets of male reproduction such as searching for mates and producing ejaculates. Nutritional status should be important to male success in the Cook Strait giant weta (Deinacrida rugosa), a flightless orthopteran insect, in which males invest considerable effort in mate searching during scrambles and transfer multiple ejaculates to female partners during a single mating bout. In this study, we hypothesize that success in scrambles for mates is related to nutritional status and thus predict that males in better nutritional condition will: (1) be more successful at finding a female, (2) find her more quickly, and (3) cover more distance per unit time during their search (i.e., have greater speed). We also predict that males in better nutritional condition will transfer more spermatophores than starved males. Although we found that critical facets of mate searching (e.g., speed) were not significantly affected by body condition, we did discover that spermatophore transfer to females was significantly related to female size and the interaction between male search effort and male body condition. We posit that perhaps males transfer spermatophores based on their current body condition and perceived mate availability. Nutritional conditon is an important factor in determining the expression of sexually selected traits in males; well-fed males produce better sexual ornaments and larger ejaculates than poorly fed males. Most studies that address this hypothesis, however, focus on species in which males display to potential female partners and then, if successful, transfer a single ejaculate to their mate. In contrast, condition could be more critical to male success in species in which males search for mates over long distances. Such scramble competition is shown by Cook Strait giant weta, where male leg length is a sexually selected trait. In this enormous insect (of conservation importance), males pass multiple ejaculates (spermatophores) to each mate; so condition in this species is also expected to be important to copulation success. Our study supports this hypothesis, but we found no evidence that mate searching speed is condition-dependent.

Melanin waterproofs mountain-dwelling weta

It can be hard to get your head around just how big some weta are if you're used to working on the Drosophila scale, but giant weta routinely tip the scales at up to 70 g and even the more diminutive tree weta tower over other more familiar insects. While some offshoots of the family make their homes in low-lying areas, others have pushed the boundaries into the mountains, where they are exposed to high winds, low oxygen, the searing sun and dry air. ‘Together, these environmental challenges…mean montane insects are at a significantly higher risk of desiccation’, say Keith King from the University of Otago, New Zealand, and Brent Sinclair from the University of Western Ontario, Canada. So how do these high-altitude insects cope with these conditions? Suspecting that they might reduce their water-loss rates, King and Sinclair set about measuring water-loss across the insect's cuticle in weta ranging from sea-level species (the Wellington tree weta, the tokoriro and the Canterbury tree weta) to the mountain dwellers (the alpine tree weta and the Banks Peninsula tree weta).The duo was impressed to see that the low-level dwellers’ cuticular water loss rate was 0.444 μmol–1 g–1 h–1 while the mountain species’ cuticular water loss rate was 45% lower at 0.245 μmol–1 g–1 h–1. They also found that the mountain dwellers had cut their respiratory water loss by 55%. And when they compared how much water the species lost relative to their metabolic rate, the mountain species were much more conservative than their low-altitude cousins, losing 64% less water.King and Sinclair then explain that the amount of melanin pigment in the cuticle of Drosophila is known to affect insect desiccation rates, with lighter flies losing water across the cuticle faster than darker species. Knowing that there are two forms of the alpine tree weta – one with a melanin-tinted cuticle and a lighter version – the duo decided to test whether the degree of melanisation affected the insects’ cuticular water loss rates. Through a direct comparison of cuticular water loss rates King and Sinclair could see that the darker form lost 46% less water than the lighter form. And when they stripped the waterproofing hydrocarbons from the surface of the cuticles of both insects and measured their cuticular water loss rates, the duo found that although the insects’ water loss rates rocketed, the darker weta still lost water 57% more slowly than the lighter insects. The high melanin content of the cuticle in the darker weta offers more protection from desiccation than the cuticle of the lighter weta.So, mountain-dwelling weta have developed various strategies to protect themselves from desiccation in their harsh mountain homes and some have probably benefited from the waterproofing effects of melanin as an unintended consequence when they became darker for camouflage.

Effective Monitoring of Arboreal Giant Weta (Deinacrida heteracanthaandD. mahoenui; Orthoptera: Anostostomatidae) using Footprint Tracking Tunnels

There are few suitable monitoring tools for assessing the effectiveness of management for threatened insect taxa. This is especially true for cryptic arboreal species of nocturnal flightless orthopterans in the genus Deinacrida from New Zealand. Systematic searching of habitat during the day was compared with footprint tracking tunnels baited with peanut butter as methods for monitoring the arboreal giant weta Deinacrida heteracantha and Deinacrida mahoenui (Orthoptera: Anostostomatidae). Searching by day required more time (3h per transect) than operating tracking tunnels (1.4h). Lines of 30–35 tracking tunnels spaced 30 m apart could be quickly set to sample large areas. Searching may provide additional information including the species, age class, and sex, whereas tracking tunnels yield presence/absence data for giant weta that were larger than other anostostomatid present. Both methods provide indices of relative abundance: it is impractical in tall forest to accurately estimate absolute density whereas tracking tunnel results are related to the activity of weta. Weta activity may depend on vapour pressure deficit modulated by the temperature. For conservation and monitoring purposes, we recommend that tracking tunnels be used first to detect giant weta and only then search for them if further data is required.

Movements, behaviour and survival of adult Cook Strait giant weta (Deinacrida rugosa; Anostostomatidae: Orthoptera) immediately after translocation as revealed by radiotracking

Giant weta (Orthoptera: Anostostomatidae) are large flightless New Zealand insects vulnerable to predation from introduced mammals. Some species have been transferred to islands or mammal-free mainland sanctuaries to establish additional populations. Radiotelemetry was used to investigate behaviour, movements and survival of adult Cook Strait giant weta (Deinacrida rugosa) immediately after translocation into Karori Sanctuary, New Zealand, to describe their initial movements, and to assess the importance of this establishment phase in relation to the long-term viability of the population. The average distance moved between consecutive daytime refuges for translocated male D. rugosa within Karori Sanctuary was significantly further than for resident weta on Matiu-Somes Island. In contrast, translocated female weta moved significantly smaller distances between consecutive daytime refuges within Karori Sanctuary than those on Matiu-Somes Island. Translocated D. rugosa travelled significantly further between consecutive daytime refuges between 19 and 45 days after release than during the first 19 days and more than 45 days of radiotracking. Deinacrida rugosa survived well following translocation and there was only limited evidence of predation despite an increased abundance of indigenous avian and reptilian predators being present, and the presence of low numbers of mice. The establishment potential of this population was not adversely affected by movements and survival of the weta immediately after translocation. It still remains to be seen if a self-sustaining population of D. rugosa develops in Karori Sanctuary but the indications are that the species is present because progeny of the translocated weta are regularly seen within Karori Sanctuary. Radiotelemetry provided valuable insights into the behaviour of adult D. rugosa and it could be appropriate for monitoring other large bodied invertebrates.

Extreme insects

A new book celebrates the extraordinary diversity of one of the planet's most diverse groups. Nigel Williams reports. A new book celebrates the extraordinary diversity of one of the planet's most diverse groups. Nigel Williams reports. Researchers interested in biodiversity could make no better start than with insects. A new illustrated book looks at the extremes in these species, highlighting just how diverse and numerous these animals are. “Through looking at insects,” the author Richard Jones says, “you can study the world — the whole natural environment — far better than you can by looking at humans. In fact, there's a lovely idea that, if an alien civilisation landed on earth and had limited time and resources to study life, all it need do is study beetles and dismiss everything else as sampling error, because you can understand the whole of evolution, ecology, genetics, physiology — the whole way life on earth works — just by studying insects.” Jones's book features images of more than 100 different insects selected to be the most extreme — the shiniest (golden chafer), the loudest (dogday cicada), the heaviest (giant weta) and shortest lived adult (mayfly), for example. “I just started with the biggest, fattest, smallest, thinnest and longest and worked from there.” He finally considered insects in three categories: extreme form, extreme evolution and extreme impact. But Jones was limited by the need to find excellent illustrations of his chosen species. “Humans now reckon themselves to be the dominant life form on earth, but we have been around for only a few hundred thousand years. Insects were here over 300 million years earlier. Humans, the mere junior upstarts, now come into conflict with much older and better established groups of organisms. And extreme insect forms are in abundance. And some have only recently been recognised. The longest insect, at more than half a metre, is the stick insect Phobaeticus chani, of Borneo, only described two years ago. Insects usually have two pairs of wings, but the flies have reduced this to one and some have none at all. But the twenty-plumed moth has divided the four true wings into a fan of ‘finger wings’ that comprise 24 plumes. And it is a moth that holds the record for the greatest wingspan: the ghost moth of Central and South America has a wingspan that can reach 305 mm. But the giant weta from New Zealand holds the record as the heaviest insect. As a flightless insect, it has put on the bulk. A female measuring just 80 mm long has been recorded at 71 grammes. In perspective, most beetles at this length probably weigh 5 grammes and birds of this size would probably weigh 12 grammes. And, of course, the colonial insects break records. Jones notes that leafcutter ants have been found to create tunnels reaching 6 metres deep and comprising between 5 and 8 million workers. More unusual is the temperature dependence of the North American snowy tree cricket's song. There are an estimated 20,000 species of crickets, katylids and grasshoppers in the world, each with its own unique song. Biologists thought the song was fixed for each species, but in 1897 the American inventor Thomas Dolbear determined that the number of calls directly related to air temperature, leading to this insect's nickname as the thermometer cricket. And Jones notes some of the most remarkable insects, in terms of their environment. Sea skaters have taken the freshwater lifestyle of their relatives to extremes. About 45 species in the genus Halobates are known; they are all tropical and mostly live inshore in mangrove swamps. But five species have been found to venture out into the open ocean. Sea skater eggs have been found on many floating objects but human rubbish appears to be attractive. In 2002, Jones reports, an empty plastic milk container dredged from the middle of the Pacific Ocean, was found to have 70,000 sea-skater eggs. While adults are often the most visible parts of the insect life cycle, their larvae can have extraordinary and lengthy lives. The golden jewel beetle larvae, Jones notes, have been shown to live more than 50 years in timber. Jones also highlights the scarab beetles, which are among the few insects that have been revered by humans. They were special for the ancient Egyptians and used as the symbol for Cheper, the god of creation. Extreme Insects Richard Jones HarperCollins ISBN: 978 0 00 731077 7

Are footprint tracking tunnels suitable for monitoring giant weta (Orthoptera: Anostostomatidae)? Abundance, distribution and movement in relation to tracking rates

Appropriate monitoring tools are essential for assessing the effectiveness of management for all threatened insect taxa. In New Zealand the large-bodied flightless orthopterans in the genus Deinacrida have mostly been monitored by searching through habitat during the day or spotlighting at night but this is time consuming and the results depend on the skill of the searcher. Recently, footprint tracking tunnels, similar to those used for monitoring small mammals in New Zealand, were found to be effective for detecting adults of various giant weta species. In this study, we compared the abundance of Cook Strait giant weta (CSGW) in the vicinity of the tunnels, estimated by mark-recapture, with the number of tracking tunnels tracked by weta. We found strong indications that both baited and unbaited tracking tunnels can be used to estimate the number of adult weta present but that this probably depends on their responses to meteorological conditions which are not yet understood. Our results also show that footprint tracking tunnels are more effective for detecting adult CSGW than searching for these insects at night and that baiting tracking tunnels with peanut butter increases their effectiveness for detecting adult CSGW. We confirmed how far Cook Strait giant weta moved each night on Matiu-Somes Island by attaching transmitters to them and found that day roosts of three adult males were on average 8.6 m apart each day and those of adult females were on average 21.3 m apart. Both the low recapture rates of marked adult CSGW and the nightly displacements of those with transmitters suggest that adult CSGW show no site fidelity and are clearly capable of moving large distances each night. However, an individual weta is unlikely to track more than one tunnel per night if tunnels are 30 m apart. Tracking tunnels have the potential to be used with some other insects, provided their footprints are diagnostic. An advantage of using tracking tunnels is that they are non-lethal and would therefore be particularly suitable for monitoring other large threatened insect taxa.

Pairing and insemination patterns in a giant weta (Deinacrida rugosa: Orthoptera; Anostostomatidae)

Positive size assortative mating can arise if either one or both sexes prefer bigger mates or if the success of larger males in contests for larger females leaves smaller males to mate with smaller females. Moreover, body size could not only influence pairing patterns before copulation but also the covariance between female size and size of ejaculate (number of spermatophores) transferred to a mate. In this field study, we examine the pre-copulatory mate choice, as well as insemination, patterns in the Cook Strait giant weta (Deinacrida rugosa). D. rugosa is a large orthopteran insect that exhibits strong female-biased sexual dimorphism, with females being nearly twice as heavy as males. Contrary to the general expectation of male preference for large females in insects with female-biased size dimorphism, we found only weak support for positive size assortative mating based on size (tibia length). Interestingly, although there was no correlation between male body size and the number of spermatophores transferred, we did find that males pass more spermatophores to lighter females. This pattern of sperm transfer does not appear to be a consequence of those males that mate heavier females being sperm depleted. Instead, males may provide lighter females with more spermatophores perhaps because these females pose less of a sperm competition risk to mates.

Morphometric change, distribution, and habitat use of Cook Strait giant weta (Deinacrida rugosa: Orthoptera: Anastostomatidae) after translocation to Matiu-Somes Island

Giant weta (Orthoptera: Anostostomatidae) are large flightless New Zealand insects in the genus Deinacrida. They usually survive in the absence of introduced rats and many have now been transferred to islands and areas after rodent eradications. One such transfer of the Cook Strait giant weta, D. rugosa was made from Mana Island to Matiu-Somes Island in 1996 and we investigated the sex ratio, morphometrics, growth, distribution, habitat use, nocturnal activity pattern and incidence of natural injury in February, May, September and December 2007 and February 2008. Most weta found were adults (82%), more adult females (74%) were seen than males but more male juveniles (61%) were seen than females. Weta from Matiu-Somes Island had slightly longer metatibiae than those from Mana Island. Cohorts of different-sized insects become larger in most successive samples indicating a 2-year development period following eclosion. Adults were always present but were most frequently seen in February when the smallest juveniles were also found, and large juveniles were common in September and December. Weta have spread throughout the island but were abundant over the northern half of the island with few found at the southern end. Adults and large juveniles were usually found on or near the ground whereas small juveniles were above ground on vegetation. Most adult weta were seen during the fi rst two hours of darkness in February on the ground or on short grass, and only five were on bushes. Overall, 22% of adults were injured, usually with damaged antennae or legs. Cook Strait giant weta are now so well established on Matiu-Somes Island that we consider this translocation a success.

Evolution: Radiotracking Sexual Selection

Why are members of one sex bigger than those of the other? A new study in which male giant weta were radiotracked found that smaller, longer legged males win the race to inseminate females.

Diversification of New Zealand weta (Orthoptera: Ensifera: Anostostomatidae) and their relationships in Australasia

New Zealand taxa from the Orthopteran family Anostostomatidae have been shown to consist of three broad groups, Hemiandrus (ground weta), Anisoura/Motuweta (tusked weta) and Hemideina-Deinacrida (tree-giant weta). The family is also present in Australia and New Caledonia, the nearest large land masses to New Zealand. All genera are endemic to their respective countries except Hemiandrus that occurs in New Zealand and Australia. We used nuclear and mitochondrial DNA sequence data to study within genera and among species-level genetic diversity within New Zealand and to examine phylogenetic relationships of taxa in Australasia. We found the Anostostomatidae to be monophyletic within Ensifera, and justifiably distinguished from the Stenopelmatidae among which they were formerly placed. However, the New Zealand Anostostomatidae are not monophyletic with respect to Australian and New Caledonian species in our analyses. Two of the New Zealand groups have closer allies in Australia and one in New Caledonia. We carried out maximum-likelihood and Bayesian analyses to reveal several well supported subgroupings. Our analysis included the most extensive sampling to date of Hemiandrus species and indicate that Australian and New Zealand Hemiandrus are not monophyletic. We used molecular dating approaches to test the plausibility of alternative biogeographic hypotheses for the origin of the New Zealand anostostomatid fauna and found support for divergence of the main clades at, or shortly after, Gondwanan break-up, and dispersal across the Tasman much more recently.

Sexual Selection for Male Mobility in a Giant Insect with Female‐Biased Size Dimorphism

Female-biased size dimorphism, in which females are larger than males, is prevalent in many animals. Several hypotheses have been developed to explain this pattern of dimorphism. One of these hypotheses, the mobility hypothesis, suggests that female-biased size dimorphism arises because smaller males are favored in scramble competition for mates. Using radiotelemetry, we assessed the mobility hypothesis in the Cook Strait giant weta (Deinacrida rugosa), a species with strong female-biased size dimorphism, and tested the prediction that male traits promoting mobility (i.e., longer legs, smaller bodies) are useful in scramble competition for mates and thus promote reproductive success. Our predictions were supported: males with longer legs and smaller bodies exhibited greater mobility (daily linear displacement when not mating), and more mobile males had greater insemination success. No phenotypic traits predicted female mobility or insemination success. In species with female-biased size dimorphism, sexual selection on males is often considered to be weak compared to species in which males are large or possess weaponry. We found that male giant weta experience sexual selection intensities on par with males of a closely related harem-defending polygynous species, likely because of strong scramble competition with other males.

Where have all the weta gone? Results after two decades of transferring a threatened New Zealand giant weta, Deinacrida mahoenui

There have been numerous transfers of the large-bodied orthopteran, the Mahoenui giant weta (Family Anostostomatidae: Deinacrida mahoenui), over the past 19 years but there has been limited follow-up monitoring to ascertain establishment and breeding of transferred populations. Recent surveys carried out at all the locations where this weta were transferred, found weta at four of the seven transferred sites. The most important factor determining the success of past transfers is the absence of introduced mammalian predators, particularly rats, at a site. At two sites, Mahurangi Island Scenic Reserve and Warrenheip, weta appeared to be flourishing and have successfully established new populations in the absence of rats. If mammals are present at a site, the occurrence of dense prickly gorse to protect giant weta from predation is another important factor in their survival. Weta were found at very low densities (only single specimens were captured) at Mangaokewa Scenic Reserve and Tikikaru (private land) and it is likely their populations are not viable in the long term. Further efforts to establish Mahoenui giant weta populations should be in mammal-free sanctuaries containing native forest. More intensive post-transfer monitoring using radio-transmitters would enable better understanding of their behaviour after transfer. In addition, long-term regular monitoring of transferred populations is required, particularly those where the likelihood of rat re-invasion is high.