Secondary poisoning of stoats (Mustela erminea) in a South Island podocarp forest, New Zealand: implications for conservation

2000 ◽  
Vol 27 (5) ◽  
pp. 501 ◽  
Author(s):  
N. Alterio ◽  
H. Moller

This study tested the efficacy of secondary poisoning using Talon 20 P™ (20 ppm brodifacoum) in bait stations for killing predators in a New Zealand podocarp forest. Nine of 10 resident radio-tagged stoats (Mustela erminea) were killed after poisoning operations that killed mice (Mus musculus), ship rats (Rattus rattus) and brushtail possums (Trichosurus vulpecula). Possums were an important source of the poison, with six stoats dying 1–2 weeks after scavenging on poisoned carcasses. New male stoats rapidly invaded the poisoned areas, but few were killed because poisoned carcasses were scarce. Most resident stoats died before possums were poisoned in other New Zealand trials when Talon 20 P was hand-broadcast. Prey abundance is potentially an important determinant of efficacy of the method, so pulse baiting is likely to be more successful than press (sustained) baiting operations for controlling stoats. Use of bait stations delayed indirect poisoning of stoats, but reduced risks to non-target native species compared with hand-broadcast operations. Talon 20 P poisoning operations using bait stations could be an especially useful way of restoring New Zealand’s mainland communities of native biota because several species of predators are killed in the same operation, but potential risks to non-target native wildlife and humans should be intensively researched before the method is routinely used. This research also demonstrates the potential hazards of the new anticoagulant poisons like brodifacoum to conservation of small native predators elsewhere.


1998 ◽  
Vol 25 (4) ◽  
pp. 419 ◽  
Author(s):  
K. P. Brown ◽  
N. Alterio ◽  
H. Moller

Two different brodifacoum (Talon 20 P™) poisoning regimes effectively killed 100% of resident radio-tagged stoats (Mustela erminea) by secondary poisoning in a New Zealand Nothofagus forest when mice (Mus musculus) were scarce. Resident possums (Trichosurus vulpecula) and ship rats (Rattus rattus) were also killed. The relative importance of different prey species as sources of poison for stoats has not been clearly identified but availability of poisoned prey will determine the efficacy of secondary poisoning in years of low prey abundance. Tracking tunnels did not accurately measure the decline in the stoat population and were probably influenced by immigrant stoats that were kill-trapped and contained high levels of poison. This study corroborates the findings of several other similar studies that secondary poisoning using brodifacoum effectively kills stoats.



2011 ◽  
Vol 38 (2) ◽  
pp. 131 ◽  
Author(s):  
Christopher Jones ◽  
Roger Pech ◽  
Guy Forrester ◽  
Carolyn M. King ◽  
Elaine C. Murphy

Context Management of suites of invasive mammal species can lead to perverse outcomes, such as meso-predator release, or can achieve desirable reductions in the abundance of top-order predators by controlling their prey. Predictive models for predator–prey systems require estimates of predator functional responses, i.e. predation rates as functions of prey density. Aims In New Zealand, estimates of the functional responses of stoats (Mustela erminea) to mice (Mus musculus) and ship (black) rats (Rattus rattus) are required to improve management models for these invasive species. Methods We derived fitted relationships between the presence or absence of mouse or ship-rat remains in stoat guts and corresponding indices of prey abundance in beech and podocarp forests, respectively. To convert field data on stoat-gut contents to minimum kill rates, we used data on feeding activity and estimates of gut-passage time, observed in captive stoats. Key results The most parsimonious fitted curves were Type II functional responses, with a steeper stoat–mouse curve for autumn–winter, indicating a more specialist feeding habit than that in spring–summer. Estimated kill rates of mice per stoat per day reached an asymptote of 1.13 during autumn–winter. Our maximum observed kill rate for spring–summer was 11% less than the extrapolated upper limit of 1.04 mice per stoat per day for New Zealand ecosystems. No asymptote was reached within the limits of the data for the stoat–rat relationship. Conclusions Recent models for trophic interactions between stoats and the primary rodent prey have overestimated kill rates by stoats in forested ecosystems, particularly at very low and very high densities of mice. We show how data on stoat-gut contents can be rescaled to estimate minimum kill rates of rodent prey. Implications The functional-response relationships we have derived can be used to improve modelled predictions of the effects of natural or management-driven perturbations of invasive stoats and their primary rodent-prey populations.



2007 ◽  
Vol 34 (2) ◽  
pp. 108 ◽  
Author(s):  
Gary W. Witmer ◽  
Frank Boyd ◽  
Zandy Hillis-Starr

The United States National Park Service and the United States Wildlife Services made a planned and sustained effort to eradicate the introduced roof rats (Rattus rattus) from Buck Island Reef National Monument in the Caribbean Sea during 1998–2000. The rats were causing substantial damage to a variety of the 80-ha island’s floral and faunal resources. An island-wide grid of elevated bait stations containing anticoagulant (0.005% diphacinone; 50 ppm) rodenticide bait blocks were used to eradicate the rats. The bait stations were modified several times to assure ready access by rats while minimising access by non-target animals, especially crabs and birds. Numerous post-project trapping sessions over six years resulted in no rat captures, suggesting that, indeed, the rats had been eradicated from the island. No non-target losses resulting from the baiting program were observed by field personnel, but they noted what appeared to be a recovery of some of the island’s floral and faunal resources. There have been no depredations of endangered sea turtle nests since the eradication. Post-project monitoring sessions revealed the presence of a growing house mouse (Mus musculus) population on the island. The threats posed by, and potential management strategies for, this introduced pest species are being investigated. This is the first successful rat eradication on a sizable island, using diphacinone bait blocks with a unique, elevated bait-station system. Diphacinone can provide an alternative to the highly toxic brodifacoum and may help reduce non-target hazards in some situations, although several applications are generally required.



2000 ◽  
Vol 22 (2) ◽  
pp. 125 ◽  
Author(s):  
D Fairbridge ◽  
P Fisher ◽  
F Busana ◽  
K Pontin ◽  
A Edwards

EXCAVATION and burying of food items is a common behaviour in canids (Saunders et al. 1999). In Victoria burial of poisonous meat baits (containing 1080) to a depth of 8 - 10 cm for red fox (Vulpes vulpes) and wild dog (Canis lupus spp.) control is a standard practice (Saunders et al. 1995; Bloomfield 1999) and is thought to provide some protection to non?target native species (Allen et al. 1989; Staples and McPhee 1995). However, black rats (Rattus rattus) have been recorded taking Foxoff� baits buried at a depth of 10cm (Dexter and Meek 1998) and anecdotal evidence indicates that native rodents will occasionally excavate and consume buried meat baits although the frequency of this behaviour is not known (H. Brunner pers. comm.).



2010 ◽  
Vol 37 (2) ◽  
pp. 89 ◽  
Author(s):  
Deborah J. Wilson ◽  
William G. Lee

Context. Rodent populations in many parts of the world fluctuate in response to resource pulses generated by periodic high seed production (masting) by forest trees, with cascading effects on predation risk to other forest species. In New Zealand forests, populations of exotic house mice (Mus musculus) irrupt after periodic heavy beech (Nothofagus spp.) seedfall. However, in alpine grasslands, where snow tussock grasses (Chionochloa spp.) also flower and set seeds periodically, little is known about house mouse population dynamics. Aims. Our primary objective was to test for an increase in alpine mouse density following a summer when snow tussocks flowered profusely. We also estimated mouse density in adjacent montane forest over 2 years, and assessed mouse diet, to predict their potential impacts on native species. Methods. Flowering intensity of Chionochloa was assessed by counting flowering tillers on permanent transects (2003–06). Mouse density was estimated with capture–mark–recapture trapping in alpine (2003–07) and forest (2003–04) habitats. Mice were also collected and their stomach contents analysed. Flowering or fruiting of alpine shrubs and herbs, and beech seedfall at forest sites, were also measured. Key results. Chionochloa flowered profusely in austral summer 2005/06. Between autumn (May) and spring (November) 2006, mean alpine mouse density increased from 4 ha–1 to 39 ha–1, then declined to 8 ha–1 by autumn (May 2007). No mice were captured in 768 trap-nights during the following spring (November 2007). Prior to the mouse irruption, mouse density was consistently higher at alpine (0.4–4.0 mice ha–1) than at montane forest (0.02–1.8 mice ha–1) sites (in 2003–04). Alpine mouse diet was dominated by arthropods before mast flowering, and by seeds during it. Conclusions. The density and dynamics of alpine mice in relation to intensive snow-tussock flowering were similar to those in New Zealand beech forest in relation to beech masts. Implications. We predict the timing and duration of periods of heightened predation risk to native alpine fauna, as the result of pulses in mouse density and likely associated pulses in the density of stoats (Mustela erminea), a key exotic predator.



2011 ◽  
Vol 279 (1733) ◽  
pp. 1597-1605 ◽  
Author(s):  
David E. Pattemore ◽  
David S. Wilcove

Reported declines of pollinator populations around the world have led to increasing concerns about the consequences for pollination as a critical ecosystem function and service. Pollination could be maintained through compensation if remaining pollinators increase their contribution or if novel species are recruited as pollinators, but empirical evidence of this compensation is so far lacking. Using a natural experiment in New Zealand where endemic vertebrate pollinators still occur on one offshore island reserve despite their local extinction on the adjacent North Island, we investigated whether compensation could maintain pollination in the face of pollinator extinctions. We show that two recently arrived species in New Zealand, the invasive ship rat ( Rattus rattus ) and the recent colonist silvereye ( Zosterops lateralis ; a passerine bird), at least partly maintain pollination for three forest plant species in northern New Zealand, and without this compensation, these plants would be significantly more pollen-limited. This study provides empirical evidence that widespread non-native species can play an important role in maintaining ecosystem functions, a role that needs to be assessed when planning invasive species control or eradication programmes.





1998 ◽  
Vol 25 (2) ◽  
pp. 133 ◽  
Author(s):  
Zane N. Moss ◽  
Cheryl E. O'Connor ◽  
Graham J. Hickling

Development of aversions, or learned ‘bait-shyness’, in frequently poisoned possum (Trichosurus vulpecula) populations is becoming increasingly detrimental to the efficacy of pest-control operations in New Zealand. This experiment aimed to identify the effects of prefeeding, a common management procedure, on the subsequent development of aversions in possums. Wild possums (n = 96) were captured and acclimatised, then allocated to one of three treatments groups that for seven days received either (i) no prefeed, (ii) plain RS5 cereal baits, or (iii) green-dyed and cinnamon-lured RS5 cereal baits. The possums were then offered a standard green-dyed and cinnamon-lured RS5 bait that contained a sublethal dose (0.4 mg kg-1) of the toxin sodium monofluoroacetate (1080). The possums were tested for development of an aversion towards a toxic RS5 1080 bait, a prefeed bait, and a prefeed bait containing an alternative toxin, brodifacoum. Most (96%) of the non-prefed possums became averse to the 1080 bait after two exposures, compared with only 55% and 9% of the two prefed groups. Similarly, 90% and 92% of the non-prefed possums were averse to prefeed and brodifacoum baits, respectively, compared with 8% and 14% of the prefed possums. This suggests that pest managers can reduce the risk of ‘bait shyness’ by prefeeding. A further advantage of prefeeding is that if poison shyness develops, use of an alternative toxin such as brodifacoum in the original bait base may still be successful.



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