A case for multi-species management of sympatric herbivore pest impacts in the central Southern Alps, New Zealand

Five herbivorous introduced mammals are sympatric in the central Southern Alps. All of these species have the potential to affect conservation values, yet the Department of Conservation at present monitors and mitigates the impacts of only one. We outline ecological arguments for multi-species management of sympatric herbivore pest impacts and use the two- species system of sympatric thar and chamois to highlight the need for multi-species management of the central Southern Alps alpine pest community.     

The effect of excesses and deficiencies in amino acids on the feeding behaviour of the common brushtail possum (Trichosurus vulpecula)

In this study of the amino acid nutrition of a marsupial we tested three hypotheses: (a) that brushtail possums eat less when diets contain excesses or deficiencies in essential amino acids, (b) that brushtail possums choose diets that do not contain amino acid excesses, and (c) that amino acid consumption is mediated partly by the 5HT3 receptor. Possums ate less when 0.2-1.0% methionine (wet matter) was added to the diet, but similar concentrations of lysine and threonine had little effect. However, when given a choice, possums always selected the basal ration over one with added lysine, methionine or threonine at concentrations between 0.05% and 0.9%. In contrast to the experiments with excess amino acids, possums did not eat less of a diet almost devoid of an essential amino acid. Instead, the possums ate less when their diets contained synthetic amino acids rather than similar amounts and proportions of amino acids as casein. Contrary to the third hypothesis, the 5HT3 receptor antagonist, ondansetron, did not affect feeding by possums given a diet containing 0.8% methionine, suggesting that post-ingestive feedback, via the 5HT3 receptor, does not regulate amino acid intake when diets contain amino acid excesses.     

Population genetics of chamois in the contact zone between the Alps and the Dinaric Mountains: uncovering the role of habitat fragmentation and past management

The chamois is a habitat specialist ungulate occupying “continental archipelagos” of fragmented rocky habitats which are frequently restricted to high altitudes. It is not clear whether forest habitats separating such population fragments act as barriers to gene flow. We studied the genetic makeup of the chamois in a topographically diverse landscape at the contact zone of two mountain ranges in Slovenia. Based on sequences of mitochondrial DNA, all Slovenian populations belong to a Northern chamois (Rupicapra r. rupicapra) subspecies. The range of chamois in Slovenia encompasses three different regions, each with unique topography, habitat connectivity and abundance of chamois: the Alps, the Dinaric Mts., and the Pohorje Mts. The habitat of the chamois is extensive and more or less continuous in the Alps, but suboptimal and fragmented in the remaining regions. In agreement with neutral genetic theory, large Northern chamois populations tended to have higher allelic richness and observed heterozygosity. Spatial clustering bears the differentiation into four geographically associated clusters within Slovenia and also revealed a strong substructure within all mountain ranges with suboptimal chamois habitat. Surprisingly, some small Dinaric populations have stayed genetically isolated in restricted habitat patches, even if they are geographically very close to each other. The four clusters, each having a unique demographic history, should be regarded as independent units for management purposes.     

Dietary Overlap Between Huemul and Livestock in Los Alerces National Park,Argentina

ABSTRACT We evaluated the potential for interspecific competition for forage between huemul (Hippocamelus bisulcus) and livestock in Los Alerces National Park, Argentina. We studied winter diets based on microhistological analysis of fecal samples. Huemul selected herbs and shrubs, sheep showed preference for herbs and grasses, and cattle selected grasses. As predicted for small-bodied species, huemul had a narrower dietary niche than did larger bodied cattle. Competition for forage would be more likely between huemul and sheep than between huemul and cattle. Our results might be helpful to managers in areas where domestic and wild ungulates live in sympatry in order to reduce competition, especially in wintering areas where food is scarce.     

Increasing Himalayan tahr and decreasing chamois densities in the eastern Southern Alps, New Zealand: evidence for interspecific competition

There is anecdotal evidence that increasing densities of Himalayan tahr (Hemitragus jemlahicus) are associated with declining densities of chamois (Rupicapra rupicapra) in the Southern Alps, New Zealand. To examine this phenomenon, densities of tahr and chamois were measured at 53 sites within their sympatric range in the eastern Southern Alps during 1978–1979. In sites where only one species was present, tahr density was significantly higher than chamois density (P=0.032), probably reflecting species differences in sociality. Chamois density was higher in catchments without tahr than in those with tahr (P=0.012). Similarly, tahr density was significantly higher at sites without chamois than at those with chamois (P=0.033). Sites with both species present (termed sympatric) were significantly larger than those with only chamois or tahr (P<0.001). Following the prohibition of aerial hunting of tahr in 1983, 16 of the 17 sites where tahr and chamois were sympatric during 1978–1979 were recounted during 1991–1996. There was a 6-fold increase in the mean density of tahr between the two counts (P=0.001), whereas chamois density had declined significantly (P=0.006). Chamois persisted at only three sites, two of which had the highest chamois densities in 1978–1979. This is evidence that increasing densities of tahr exclude chamois from all but the `best' habitats. We conclude that intensive aerial hunting of tahr during 1967–1983 reduced tahr densities such that chamois could co-exist with tahr. Received: 20 March 1997 / Accepted: 8 September 1997     

Population genetic structure of Alpine chamois <Emphasis Type="Italic">(Rupicapra r. rupicapra)</Emphasis> in the Italian Alps

Analysis of the genetic diversity of the Alpine chamois in Italy was conducted using a pool of 26 microsatellite loci. A total of 209 animals were analyzed, representing six geographical populations from different location of the Southern slope of the Alps. Clear genetic differences have emerged between the sampled chamois groups. Some were consistent with an isolation-by-distance model. However, in parallel, other mechanisms intervened in areas that, in addition to being peripheral to the main alpine ridge, had suffered from recent bottlenecks. In such areas, genetic drift and a low rate of gene flow are likely explanations for the current genetic structure.     

Food–niche relationships within a guild of alpine ungulates including an introduced species

To assess competition for trophic resources within a guild of ungulates, we studied the food niches of sympatric ungulates in an alpine area of the Italian Western Alps and evaluated the extent of their dietary overlap, especially with regard to the presence of the introduced mouflon Ovis musimon . The roe deer Capreolus capreolus had the most diverse diet including dicotyledons, young sprouts of trees and an unusually high percentage of graminoids. The red deer Cervus elaphus and chamois Rupicapra rupricapra mainly consumed graminoids, supplemented with dicotyledonous herbs and woody plants. The mouflon was a grass feeder, with graminoids representing the majority of items ingested in all seasons. Among the native species, we recorded a high overlap of feeding choices between red deer and chamois, which frequently used the same areas and are both intermediate feeders. The mouflon showed considerable dietary overlap with the chamois and red deer in all seasons, while the similarity with roe deer was low. High food–niche overlap can imply competition but only if resources are limited and the species use the same habitats.     

Acid loads induced by the detoxification of plant secondary metabolites do not limit feeding by common brushtail possums (Trichosurus vulpecula)

We fed common brushtail possums artificial diets containing a buffer and the plant secondary metabolite (PSM), orcinol, to test the hypothesis that organic acids, common products of PSM metabolism, limit feeding by common brushtail possums (Trichosurus vulpecula). We introduced several diets containing orcinol and a buffer (urinary alkalising agent) over a course of three experiments. A diet containing 2% orcinol (wet matter) caused possums to reduce their food intake immediately, but feeding returned to normal 1–2 days later. Even though possums excreted strongly acidic urine (pH 5.1) and had perturbed nitrogen metabolism, they maintained their food intake and body mass until the experiment terminated 9 days after the introduction of orcinol. Possums ate 52% less when the basal diet contained 4% orcinol. As expected, the acid loads caused a change in the composition of urinary nitrogen with possums excreting more ammonium than urea and a large amount of unidentified nitrogenous material. Supplementing the diet containing orcinol with buffer neutralised the metabolic acid load and partly restored normal nitrogen metabolism, but did not restore feeding. Also, animals eating orcinol excreted normal amounts of 3-methylhistidine, indicating no increase in muscle protein catabolism. This suggests that a limitation to the rate of detoxification or toxicosis, rather than acid loads, limits the ingestion of acid-inducing PSMs.     

Intraspecific differences in the diet of Antarctic fur seals at Nyrøysa, Bouvetøya

Intraspecific differences in the diets of many species of pinnipeds are to be expected in view of the great differences in morphology, life history and foraging behaviour between the sexes of many species. We examined the diet of the Antarctic fur seal population at Bouvetøya, Southern Ocean, to assess intersexual differences. This was made possible by the analysis of prey remains extracted from scats and regurgitations collected in areas used primarily by one or the other sex. The results indicate that both males and females feed primarily on Antarctic krill Euphausia superba with several species of fish and squid being taken, likely opportunistically given their prevalence. Significant differences were identified in the frequency of occurrence of otoliths in scats and the percentage numerical abundance of the major fish prey species in the diet. Adult males ate a smaller quantity of fish overall, but ate significantly more of the larger fish species. The greater diving capabilities of males and the fact that they are not limited in the extent of their foraging area by having to return regularly to feed dependant offspring may play a role in the differences found between the diets of males and females. Additionally, females might be more selective, favouring myctophids because they are richer in energy than krill. The absence of major differences in the diet between the sexes at this location is likely due to the high overall abundance of prey at Bouvetøya.     

Role of feeding and prey distribution of summer and southern flounder in selection of estuarine nursery habitats

Diets of metamorphosing larvae and early juvenile summer and southern flounder were examined during the settlement period when their distributions overlapped and during a subsequent period when the two flounders were found in different habitats. Prey abundance on tidal flats was examined along an upstream transect. Though initially similar, diets of the two species diverged prior to the development of a segregated distribution. These diet differences reflected those found in the diets of the two species following segregation. Southern flounder ate more active epifaunal prey: mysids, amphipods and calanoid copepods and appeared to be an ambush predator. The summer flounder ate primarily infauna: polychaetes, and invertebrate parts and appeared to be an active forager. Distribution of prey within the study area suggested that mysid gradients may influence movement of southern flounder to nursery grounds. The coupling of biotic and abiotic gradients are probably important in creating nursery areas and guiding fishes to species specific habitat types.     

Identifying eradication units in an invasive mammalian pest species

Eradication of invasive species is an important component for species conservation and ecosystem restoration. Success of eradications is dependent on knowledge of population connectivity in order to determine reinvasion pathways, and hence populations requiring simultaneous eradication (eradication units). The common brushtail possum (Trichosurus vulpecula) was introduced into New Zealand from Australia and Tasmania, and now occupies a wide range of habitats across the majority of New Zealand. Possums are one of the most destructive invaders within New Zealand, with extensive control operations occurring throughout the country. Understanding the population connectivity of possums on mainland New Zealand (North and South Islands) will enhance the success of planned eradications. We examined the genetic population structure of invasive possums to identify gene flow, thus reinvasion pathways, between seven populations around Dunedin and on the Otago Peninsula where eradication of possums is occurring. Genetic variation at 12 microsatellite loci was comparable between all sampled populations and exhibited a significant isolation by distance pattern. Bayesian clustering methods supported the existence of two population clusters, indicating the presence of a reinvasion pathway onto the Otago Peninsula from urban areas at the Southern end of the Peninsula. To avoid recolonisation, all possums on the Otago Peninsula should be eradicated simultaneously, with the implementation and ongoing maintenance and monitoring of an urban buffer zone. We recommend pre-eradication genetic analyses be adopted by all pest managers to define appropriate eradication units, thereby maximising eradication success and avoiding costly failures.     

Intraspecific and seasonal differences in the diet of feral ferrets (

This study reports the diet of feral ferrets (Mustela furo) in a pastoral habitat, East Otago, South Island, New Zealand. Rabbits (Oryctolagus cuniculus) were the most common prey of ferrets, occurring in 86.7% of seats, but birds (12.4%) and invertebrates (11.3%) were also frequently eaten. Female ferrets ate more non-lagomorph prey items, especially invertebrates and birds than males. No significant dietary differences were found between juvenile and adult ferrets except in summer when juveniles ate more lagomorph prey. There were seasonal differences in the consumption of rabbits, invertebrates, skinks, possums (Trichosurus vulpecula) and small and large secondary prey items. Seasonal differences in ferret diet are likely to be related to the relative abundance of the various prey items. Lagomorph availability may also be a determinant of the frequency of occurrence of other prey items in the diet. Dietary differences may differentially influence the functional response of adults and juveniles and/or males and females to rabbit control or other manipulations of prey populations. Bovine tuberculosis (Mycobacterium bovis) infections in ferret populations show intraspecific variation with more males than females and more adults than juveniles infected. Intraspecific dietary differences in diet were not observed in the species (possums and hedgehogs (Erinaceus europaeus)) considered to be the main sources of infection for ferrets.     

Diet and impacts of brushtail possum populations across an invasion front in South Westland, New Zealand

Impact of the irruptive fluctuation in abundance of brushtail possum populations since their initial colonisation was investigated in the forests of South Westland, New Zealand. Possum abundance, fecundity, and diet, the condition of common possum-palatable tree species, and the abundance of common forest birds were measured at three sites occupied by possums for c. 10, 20, and 30 years. Possum densities were highest at the site where possums had been present for c. 20 years. Possum fecundity was higher at the site they had recently colonised than at the two sites where they had been present for c. 20–30 years. Diet of possums where they had recently colonised was dominated by highly preferred foods (72% of total diet), whereas these same foods contributed just 36% of total diet at the site where possums had been present for more than two decades. Canopy condition of common possum-preferred trees was scored progressively lower in areas with increasing length of possum occupation, especially at the site where the possum population had apparently declined from its maximum density. Native forest bird abundance also declined with increasing length of possum occupation. The implications of these results for management are discussed.     

FOOD HABITS OF WILDEBEEST, ZEBRA, HARTEBEEST AND CATTLE IN KENYA MASAILAND

A study was conducted of grass selectivity shown by four herbivores on open range lands of Kenya Masailand. At four seasons over one year, wildebeest, zebra and kongoni (Coke's hartebeest) were taken. Stomach materials and faeces were sampled from each animal. Faecal samples were collected from cattle that had been grazing in the same area. Simultaneously, vegetation availability assessments were made. A comparison of techniques for determining the food selectivity indicates that faecal and stomach-content analyses provide similar results when the diets are almost entirely grass. The selectivity exhibited by the four herbivores was determined by faecal analyses. Three grass species were preponderant in all diets as well as in the available menu. In comparing the selectivity shown for the three dominant grasses there is a high degree of similarity even though statistical differences are demonstrated. All animals favoured Themeda triandra over Pennisetum mezianum and Digitaria macroblephara. Kongoni displayed the highest degree of selectivity and cattle and zebra had the greatest similarity in diets. Each animal species had a wide spectrum of grasses in their diets: these contained a greater number of species during the drier seasons than during the rainy seasons. Wild animals had a greater diet variation between seasons than did cattle, the diet of the latter remaining much more consistent than the combination of available grasses.     

The Enhanced Vegetation Index (EVI) as a proxy for diet quality and composition in a mountain ungulate

In recent years, the use of satellite-derived vegetation indices has become a powerful tool to collect information on vegetation dynamics in a broad range of ecosystems worldwide. However, the utility of these indices as indicators of the diet composition and quality of herbivore mammals has not yet been established. This work focuses on exploring such relationships analysing four years of records of monthly Enhanced Vegetation Index (EVI, a MOD13 satellite-derived index) and diet composition and quality of two populations of chamois (Rupicapra pyrenaica pyrenaica) in the Eastern Pyrenees (Spain). Our results revealed that 68.4% and 53.3% of diet composition and quality of chamois can be explained by EVI values in the green-up season (spring) and green senescence (winter season), respectively. In both periods, EVI was related mainly to diets low in fibre (cellulose, hemicellulose and lignin) and heather (Calluna vulgaris) and high in nitrogen due to the consumption of Festuca, Forbs and Trifolium. During the summer season however, the EVI was not significantly related to diet components of chamois. A significant inter-year variability in the diets of the chamois was also observed. To conclude, remote sensing is appropriate to assess temporal variations in dietary components of mountain ungulates, and could be used as a component of monitoring large herbivore populations in management programmes.     

Feeding habits,forage selection,and diet overlap in Alpine chamois (<Emphasis Type="Italic">Rupicapra rupicapra</Emphasis> L.) and domestic sheep

Fecal microhistological analyses have been used to assess the summer diet of chamois (Rupicapra rupicapra L., 1758) and domestic sheep and to evaluate diet overlap. The aim of our work was to investigate interspecific interactions and to assess the effects of sheep grazing on the summer feeding habits of chamois. A high dietary overlap (Pianka’s index = 0.93–0.99) was found, despite differences in the use of some plant groups. Sheep presence strongly affected chamois feeding habits: a reduction of highly digestible forbs was observed in the chamois diet during August, when both species grazed in the same range. As a consequence of sheep grazing, chamois may have been forced to reduce niche breadth and to change their food habits, increasing percentages of monocotyledons in the diet and feeding mainly on Cyperaceae. The diet overlap between sheep and chamois suggests that resource-mediated interactions as well as direct competition must be taken into account when evaluating chamois and sheep compatibility on Alpine meadows.     

Comparative evaluation of effort, capture and handling effects of drive nets to capture roe deer (Capreolus capreolus), Southern chamois (Rupicapra pyrenaica) and Spanish ibex (Capra pyrenaica)

The objective of this study is to assess the usefulness of drive nets to capture roe deer (Capreolus capreolus), Southern chamois (Rupicapra pyrenaica) and Spanish ibex (Capra pyrenaica), comparing the results obtained with other capture methods and amongst the three species. Sixty-five drive net capture operations using beaters were conducted from January 1998 to September 2004. A total of 161 wild ungulates (31 roe deer, 95 Southern chamois and 35 Spanish ibexes) were captured. The average number of animals captured per operation was 1.07 for roe deer, 3.96 for Southern chamois and 2.92 for Spanish ibex. The average number of person–days per captured animal was 21.5, 7.1 and 10.6 for roe deer, Southern chamois and Spanish ibex, respectively. Specificity was 100% for Southern chamois and Spanish ibex (only the target species captured) and 77.5% for roe deer. Risk for the animals (mortality plus injuries) was 3.23% for roe deer, 5.27% for Southern chamois and 0% for Spanish ibex, whereas injuries to the operators occurred with 3.1% of the handled animals. Sex ratio was skewed towards females in roe deer, towards males in Southern chamois and balanced in Southern chamois. Drive nets showed good performance, although many operators were required. Safety for the animals and specificity were higher than traditionally attributed to this capture method. It is concluded that drive nets are an efficient and safe method to capture many ungulate species.     

A severe episode of wildlife-derived scabies in domestic goats in Italy

A scabies outbreak, with unusually high mortality and morbidity, occurred in a poorly managed goat flock in north-eastern Italy. The source of infection was traced back to contact with scabietic chamois (Rupicapra rupicapra) within a recognised sylvatic focus of the disease. Spill-over of scabies from chamois to goats is a matter of great concern to resource managers. Currently scabies-free populations of wild Caprinae in the central and western Alps may eventually be exposed to infected goats transported over long distances. Sanitation of the studied flock was obtained following three applications of pour-on moxidectin at an approximate dose of 500 mcg/kg. Follow-up included titration of circulating anti-Sarcoptes antibodies in a labelled avidin–biotin ELISA test. Two operators developed pseudoscabies after handling the infested flock.     

Analysis of the characteristics of fruit eaten by possums,Trichosurus vulpecula,in New Zealand

Abstract

The colours and sizes of the fleshy fruits of native trees and shrubs in the New Zealand flora and in the flora of the Orongorongo Valley, southern Rimutaka Range, were compared with those known to be eaten by possums to assess the degree of food selection by possums. Colour and diameter of fruits had little effect on whether they were selected by possums, but the size of the enclosed seed affected feeding behaviour. Fruits with seeds < 10 mm were eaten whole, whereas usually only the skin and flesh were eaten from fruits with larger seeds. An analysis of the wet and dry weights of the flesh and seeds of fruits growing in the Orongorongo Valley suggested that possums could maximise their dry matter intake from fruits by feeding preferentially on the larger fruits. Although this suggestion was supported in general by field observations, other studies suggest that annual variations in the abundance of fruits of the various species and their accessibility are also important in determining the contribution of fruits to the diet of possums.     

Browse on mahoe and kamahi leaf-fall as a trigger for possum control

Introduced brushtail possums (Trichosurus vulpecula) are controlled over large parts of New Zealand to protect canopy trees. The condition of canopy trees is one of the cues used to trigger possum control, but selecting an indicator of canopy tree condition is difficult because many factors unrelated to possum browsing can affect canopy condition, and indices based on canopy scoring may not always quickly detect real changes in possum herbivory. We therefore investigated the usefulness of the percentage of fallen mahoe (Melicytus ramiflorus) and kamahi (Weinmannia racemosa) leaves browsed by possums (‘fallen-leaf browse’ or ‘FLB’) as a trigger for control aimed at protecting these tree species. We collected leaves falling from kamahi and mahoe trees every two months for two years at two study areas in the central North Island, one with initially high possum abundance (Oriuwaka) and the other with low possum abundance (Otupaka). We classified each of 92 384 leaves as either not-browsed, possum-browsed or insect-browsed. There was a strong and similar seasonal pattern in the mean number of fallen leaves per tree for both mahoe and kamahi at both study areas; fewest leaves fell in winter, and the most leaves fell in spring and early summer. Mahoe and kamahi FLB exhibited a similar seasonal pattern at both areas, being lowest in winter and highest in spring and early summer. FLB for both mahoe and kamahi declined following control of possums to low densities at Oriuwaka. The proportion of fallen mahoe and kamahi leaves browsed by possums was small compared with those browsed by insects or not browsed. We show that spring/early summer (i.e. September–December) is the best period for sampling FLB and that the mean FLB can be estimated with a CV of 20% if one trap is randomly placed under the canopy of each of 24 randomly located trees. However, CVs were much larger in other seasons and when possum abundance was low. We consider FLB to be a sensible trigger for initiating possum control when the objective of control is to protect canopy trees, but further work is needed to determine the relationships between possum abundance, FLB, canopy condition, and key tree demographic rates.