Takahe Research Articles

Immediate and long-term effects of translocations on breeding success in Takahe Porphyrio hochstetteri

Translocations of threatened species play an increasingly important role in conservation management. However, few studies have examined what effects, if any, the translocation process itself (i.e. catching, handling, confining, transferring and releasing an animal into an unfamiliar environment) has on subsequent breeding success. Takahe Porphyrio hochstetteri living on offshore “predator-free” islands in New Zealand are a model system for examining such effects because pre-breeding birds have been frequently translocated between established island populations before they pair up and breed at 2-3 years of age. We postulated that “translocated” breeders (i.e. breeders that had been raised on another island) would delay first breeding attempts and/or have lower reproductive success compared with “resident” birds (i.e. bred on the same island that they were raised). The results indicated that translocated birds did not delay breeding and had similar mean hatching and fledging success as resident pairs in their first breeding season and subsequent seasons combined. The results suggest that at least for large or long-lived birds such as Takahe, the effects of any stress from the translocation itself, or the release into an unfamiliar environment, might be either short-lived or not significant enough to hinder subsequent breeding success. We recommend that further research be carried out on other species to determine the baseline effects, if any, of translocations, so that they can be taken into account when considering other determinants of translocation success such as habitat suitability, number of individuals and timing of releases.

Sex‐Specific Consequences of Recent Inbreeding in an Ancestrally Inbred Population of New Zealand Takahe

Abstract: Although the negative effects of close inbreeding in captive populations are well known, inbreeding in small, free‐ranging populations is less well understood. During the mid‐1980s, small numbers of the flightless Takahe ( Porphyrio hochstetteri ) were successfully translocated from the last remaining population in mountainous Fiordland to four island refuges. Previous research has shown that introduced island Takahe and their descendents lay significantly more infertile eggs and raise fewer juveniles per egg than Takahe in their native habitat in Fiordland. Here we first show that the remnant population of Takahe in Fiordland was likely to have been severely inbred. From this we hypothesize that further, recent inbreeding ( based on four generations of pedigree data ) by Takahe on islands should have negligible fitness consequences. This hypothesis is only partially supported. Mean hatching and fledging success has remained consistently low ( <40% and 77%, respectively ) and was not correlated with the rapid increase in the average inbreeding coefficient of island Takahe since 1991. Neither the inbreeding coefficient of a pair's offspring nor the inbreeding status of the breeding male had a significant effect on hatching or fledging success. Similarly, the inbreeding status of the breeding female had no significant effect on hatching success. However, the inbreeding status of the female did negatively affect fledging success. Why poor reproductive success was further exacerbated by inbreeding in females but not in males or pairs is unknown, although a similar pattern has been reported in an island population of Song Sparrows ( Melospiza melodia ). We speculate that the generally lower reproductive success that most island Takahe exhibit is a result of environment‐dependent inbreeding depression. We conclude from our pedigree analysis that island Takahe are undergoing further inbreeding depression, but the reduction in fitness appears to be expressed in inbred females only.

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 takahe's 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.

Increased egg infertility associated with translocating inbred takahe ( Porphyrio hochstetteri) to island refuges in New Zealand

The takahe ( Porphyrio hochstetteri) is a highly endangered flightless rail, endemic to New Zealand. Since 1984, a total of 24 takahe have been translocated from a small, alpine population of approximately 120 in Fiordland and successfully established on four predator-free lowland islands with introduced pasture grasslands. However, island takahe produce fewer juveniles per egg due to hatching failure being twice as high as it is in the natural population in Fiordland. A comparison among several small, inbred populations of New Zealand birds indicated those that are the result of translocations to new habitat types (takahe and kakapo Strigops habroptilus), suffered much higher rates of egg infertility than birds that have remained within their natural habitat range. For takahe, whether breeders had been translocated as juveniles or had been raised on the islands was a poor predictor of reproductive success. The coefficient of inbreeding was high for island takahe but high infertility and low juvenile productivity were features of breeding pairs whether parents were related or not. However, this result might be expected if takahe were already inbred before they were translocated to the islands. If high egg infertility is a consequence of an inbred population being translocated to a new or different habitat, then poor breeding success is something that managers may have to live with in the short term until there is local selection for better breeders. In more general terms, the results of the study have implications for the successful translocation of individuals from inbred populations.

Detecting sperm on the perivitelline membrane of incubated turkey eggs and its implications for research on fertility problems in endangered species

A method whereby sperm nuclei on the perivitelline membrane are stained and counted under a photomicroscope has been used extensively in the poultry industry to show a correlation between egg infertility and low numbers of spermatozoa near the site of fertilisation. It has been suggested that this method could also be potentially useful for assessing infertility problems in endangered species. For poultry, the staining technique is normally applied to fresh (i.e. unincubated) eggs, but conservation managers normally collect eggs for examination only after they have been incubated for several days and then assessed (by candling) to lack a developing embryo. Whether sperm would persist on the perivitelline membrane of infertile eggs incubated over several days is not known. In relation to our research on egg infertility in the endangered takahe (Porphyrio hochstetteri), we examined the above problem by comparing sperm counts on the membrane of fresh versus incubated infertile eggs from artificially inseminated domestic turkey (Meleagris gallopavo). We were able to detect sperm in most infertile eggs that had not been incubated, but no sperm at all were detected in infertile eggs that were incubated for seven days, suggesting that warming of the eggs may cause the sperm on the membrane to degrade. The inherent fragility of avian sperm nuclei may limit the usefulness of this technique for assessing infertility in takahe and other species where failed (non-developing) eggs are not removed from the nest until after a short period of incubation.

Morphology and evolution of two takahe: flightless rails of New Zealand

Two forms of a large and flightless rail (takahe) belonging to the genus Porphyrio and endemic to New Zealand have been described, although their taxonomy has been repeatedly questioned. Analyses of osteometric data from modern and Quaternary fossil material show such a degree of allometric distinctiveness that it is considered that the two forms are, indeed, different species as originally described, Porphyrio mantelli (Owen), Porphyrio hochstetteri (Meyer). It is suggested that this degree and type of difference could have resulted from the two species arising independently from similar volant ancestors.

Food Selection by Takahe Notornis mantelli in Relation to Chemical Composition

Selective feeding by the Takahe Notornis mantelli, an endangered, flightless, herbivorous rail, endemic to New Zealand, was studied in the Murchison Mountains, Fiordland, between 1976 and 1980. Takahe occupy the alpine grasslands throughout the snow-free period and have a simple diet consisting of leaf bases of snow tussock grasses (Chionochloa pallens, C. flavescens, C. crassiuscula) and a mountain daisy Celmisia petriei. Changes in seasonal diet between plant species and between plants of the same species were examined in relation to the mineral nutrient, carbohydrate, lipid and soluble sugar content. Tussock species eaten by Takahe contained more nitrogen, phosphorus, potassium, calcium, sodium and soluble sugars than those eaten less frequently or avoided, but selection for specific nutrients changed seasonally. Takahe selected within and between species for high concentrations of nitrogen and phosphorus in spring-early summer, and for carbohydrates in late summer-early autumn. Amongst the tussock grasses, the birds displayed a preference for actively growing, nutrient-rich tissue and appeared to differentiate between species and among sites along an altitudinal gradient to take advantage of interand intra-specific differences in the onset of growth flushes. Takahe also favoured leaf bases of flowering tussock tillers. Observations of Takahe feeding behaviour on Chionochloa pallens showed that the birds sampled widely before intensively feeding on a tussock. It is suggested that the basis for food selection involves discrimination by visual qualities and chemical cues associated with taste.

Experimental Investigations of the Effects of Takahe and Deer Grazing on Chionochloa pallens Grassland, Fiordland, New Zealand

(1) The takahe (Notornis mantelli Owen), an endangered flightless rail, restricted to the Murchison and Stuart Mountains of Fiordland National Park, New Zealand, shares the alpine snow tussock grasslands with introduced red deer (Cervus elaphus L.) in summer. The herbivores eat the same tussock species but, whereas takahe pull out tussock tillers and eat only the succulent basal butt portion of the tiller, deer eat the leaf blades. (2) Experimental manipulations of individual Chionochloa pallens Zotov tussocks simulating the feeding mode of deer and takahe were undertaken to evaluate the effects of each herbivore, and the combined effect of both, on the productivity and nutrient status of the plants. Tussocks cut to simulate deer grazing were monitored to assess whether and when takahe would eat deer-grazed tussocks. (3) The feeding by takahe on cut tussocks was largely confined to autumn and winter, when the starch content of these tussocks was higher than that of uncut tussocks. The combined effect of takahe feeding and the cutting induced a long-term decline in the biomass of the tussocks. Eight and a half years after cutting, the biomass of the cut tussocks was 64%/o less than that of uncut tussocks. It was estimated that it would take 20 years for the tussocks to recover, even if no further grazing occurred. (4) Pulling 25 and 50%/o of tillers from C. pallens tussocks in the manner that takahe feed caused no significant decline in tillering rates in a non-flowering year. However, severe cutting of tillers at the blade-sheath junction, with or without pulling, invariably caused a decline in tillering. (5) Competition for food with deer has played a major role in the decline of takahe since it was rediscovered in 1948. Intensive deer control operations since 1962, particularly in the early 1 970s, reduced deer numbers appreciably. It is suggested that the long lag period between the decline in deer grazing pressure on the grasslands and the beginning of the recovery of the takahe population in 1982 reflects the 15-20-year recovery time needed for the preferred tussock species to recover. (6) To avoid long-term detrimental effects on takahe habitat, continued deer control is necessary because the rate of habitat degradation through deer grazing is much more rapid than the recovery time.

The karyotype of Notornis mantelli (takahe)

Abstract The karyotyping of the endangered takahe (Notornis mantelli) is reported. Sex identification of this species, which exhibits no sexual dimorphism, is determined by counting the number of macrochromosomes and Z sex chromosomes in the metaphase spreads. The second sex chromosome (W) was not identified by Giemsa staining. The karyotype of N. mantelli was compared with the related species F. atra and G. chloropus and only minor differences were observed.

The subfossil deposits of Paryphanta (Mac's Quarry) Cave, Waitomo

Abstract The stratigraphy and sedimentology of the fluvial deposits of a limestone fissure cave in the Waitomo district, western North Island, are described. A microflora, from 60 cm depth and possibly of Otiran age, indicates the former presence of lowland mixed broadleaf-podocarp forest. Faunal remains, found only in the uppermost 25 ern of the deposits, are probably no older than Holocene. Every member of the fauna, comprising 14 species of land bird, a skink, at least one species of frog and 13 species of land snail, inhabited forest. Fewer than half the bird species represented in the subfossil deposits currently inhabit the area, owing primarily to human clearance of indigenous forest. Three species, Notornis mantelli, Strigops habroptilus and Notiomystis cinca, now have exceedingly reduced distribution, and two others, Fulica chathamensis and Megaegotheles nooaezealandiae, are extinct.