Steven J. Lapidge

Comparison of methods to detect rare and cryptic species: a case study using the red fox (Vulpes vulpes)

Choosing the appropriate method to detect and monitor wildlife species is difficult if the species is rare or cryptic in appearance or behaviour. We evaluated the effectiveness of the following four methods for detecting red foxes (Vulpes vulpes) on the basis of equivalent person hours in a rural landscape in temperate Australia: camera traps, hair traps (using morphology and DNA from hair follicles), scats from bait stations (using DNA derived from the scats) and spotlighting. We also evaluated whether individual foxes could be identified using remote collection of their tissues. Genetic analysis of hair samples was the least efficient method of detection among the methods employed because of the paucity of samples obtained and the lack of follicles on sampled hairs. Scat detection was somewhat more efficient. Scats were deposited at 17% of bait stations and 80% of scats were amplified with a fox-specific marker, although only 31% of confirmed fox scats could be fully genotyped at all six microsatellite loci. Camera trapping and spotlighting were the most efficient methods of detecting fox presence in the landscape. Spotlighting success varied seasonally, with fox detections peaking in autumn (80% of spotlighting transects) and being lowest in winter (29% of transects). Cameras detected foxes at 51% of stations; however, there was limited seasonality in detection, and success rates varied with camera design. Log-linear models confirmed these trends. Our results showed that the appropriate technique for detecting foxes varies depending on the time of the year. It is suggested that wildlife managers should consider both seasonal effects and species biology when attempting to detect rare or elusive species.

Using Baits to Deliver Pharmaceuticals to Feral Swine in Southern Texas

Abstract Few studies have evaluated oral delivery systems of pharmaceuticals (e.g., vaccines, fertility control agents, and toxicants) to feral swine (Sus scrofa) in the United States. Our objective was to assess, through a field trial, the percentage of feral swine and nontarget animals that remove and consume baits intended to transport pharmaceuticals to feral swine in southern Texas, USA. We hand-placed 1,178 iophenoxic acid (IA)–marked baits distributed over 1,721 ha (68 baits/km2) in April 2005 and monitored species-specific bait removal and consumption using track stations, automated camera systems, and serum IA values from captured animals. Ninety percent of baits were removed after 72 hours. For baits for which we determined the species that “definitely” or “likely” removed bait using track stations and cameras, 51% were taken by raccoons (Procyon lotor), 22% were taken by feral swine, and 20% were taken by collared peccaries (Tayassu tajacu). We found elevated serum IA values in 74% of trapped feral swine, 89% of raccoons, and 43% of opossums (Didelphis virginiana). Our oral delivery system was successful in marking a substantial proportion of feral swine. However, our observed removal rates suggest that the majority of the baits were taken by nontarget species and, therefore, unsuitable for most pharmaceutical applications in their current form.

Using a general index approach to analyze camera-trap abundance indices†

ABSTRACT The lack of variance estimates constrain the utility of abundance indices calculated from camera-trap data. We adapted a General Index model, which allows variance estimation, to analyze camera-trap observations of feral pigs (Sus serofa) for population monitoring in a tropical rainforest. We tested whether the index would respond to population manipulation, and found that it decreased by 57% following removal of 24 pigs and remained low in the following period. Our method is useful for monitoring other large animals in difficult landscapes, and the model can be used to enhance the value of existing data sets.

Additional toxins for feral pig (Sus scrofa) control: identifying and testing Achilles’ heels

A literature review was conducted in order to identify unique weaknesses in the physiology or metabolism of pigs that could be targeted with specific chemicals (i.e. an ‘Achilles’ heel’ search). A promising weakness identified was the species’ susceptibility to methaemoglobin-forming compounds, most likely related to their uniquely low levels of methaemoglobin reductase. Further examination revealed that sodium nitrite is a cost-effective, readily available methaemoglobin-forming compound that is highly toxic to domestic pigs, which has caused numerous accidental poisonings. Pen trials on pigs showed that sodium nitrite delivered by gavage (>90 mg kg-1) and freely consumed in bait (>400 mg kg-1) caused rapid and lethal rises in methaemoglobin. Sodium nitrite appeared to be more humane than currently used toxins, with deaths following bait consumption being considerably quicker and with fewer symptoms (within 80 min of clinical signs beginning; clinical signs including infrequent vomiting, lethargy, ataxia and dyspnoea). The review also identified a second deficiency in the metabolism of pigs, namely high sensitivity to selective inhibition of cytochrome P450 liver enzymes. This leads to potentially lethal interactions between various drugs, such as two antibiotics, monensin and tiamulin. A pen trial confirmed that the antibiotic combination in a single gavage dose was reliably and rapidly lethal to pigs. However, its utility as a pig toxin is low, because it was unpalatable to pigs when delivered in bait and appeared to cause pain and suffering (leading to the early termination of pen trials). The findings presented here demonstrate the potential of sodium nitrite as an additional feral pig toxin.

Efficacy of manufactured PIGOUT® baits for localised control of feral pigs in the semi-arid Queensland rangelands

Conservative population declines of 73% were recorded in three independent feral pig populations in Welford National Park, Queensland, when PIGOUT® baits containing 72 mg of sodium fluoroacetate were used in a baiting program following prefeeding. Declines were measured using a prebaiting population census with remote cameras, followed by carcass recovery. The knockdown of susceptible feral pigs may have been higher than this, since any carcasses not recovered reduced the recorded efficacy. In addition, feral pigs know to have left the baiting area after trapping and telemetry-tagging, and subsequently not exposed to toxic baits, were included in the analysis. The use of remote cameras and carcass recovery appears to be a relatively accurate means of recording localised declines in feral pig populations. This method is applicable only when carcass recovery is possible, such as in open areas in the semi-arid rangelands. A decline of 86% of radio-tagged feral pigs attending bait stations was also recorded. Camera observations revealed no non-target consumption of baits. Measurement of sodium fluoroacetate–contaminated tissues from feral pigs showed that residues were too low to present a significant risk to recorded scavenging animals in the area. Some feral pigs vomited before death, with vomitus containing sodium fluoroacetate poison at high concentrations. No vomitus was consumed by non-target species. Almost all feral pigs were killed relatively rapidly after ingestion of sodium fluoroacetate and the signs observed in a small number of poisoned feral pigs did not indicate a significant welfare concern.

A review of existing and potential New World and Australasian vertebrate pesticides with a rationale for linking use patterns to registration requirements

Registration is a necessarily sophisticated evaluation process applied to vertebrate pesticide products. Although conducted to minimise any potential impacts upon public health, the environment and food production, the all-encompassing process of registration can stifle innovation. Vertebrate pesticides are rarely used to control pest animals in food crops. In contrast to agrochemicals, relatively small amounts of vertebrate pesticides are used (<0.1%), usually in solid or paste baits, and generally by discrete application methods rather than by broad-scale spray applications. We present a hierarchy or sliding scale of typical data requirements relative to application techniques, to help clarify an evolving science-based approach which focuses on requiring data to address key scientific questions while allowing waivers where additional data have minor value. Such an approach will facilitate the development and delivery of increasingly humane, species-targeted, low residue pesticides in the New World, along with the phasing out of less desirable chemicals that continue to be used due to a lack of alternatives.

Attractiveness of a novel omnivore bait, PIGOUT®, to feral pigs (Sus scrofa) and assessment of risks of bait uptake by non-target species

Following a bait-preference pilot study on captive feral pigs, a series of field studies assessed the attractiveness and target-specificity of a prototype manufactured feral pig bait (PIGOUT®). Two promising test baits and fresh meat reference baits were biomarked with iophenoxic acid and aerially distributed in 100-km2 blocks of land infested with feral pigs in western Queensland to assess field uptake and target-specificity without prefeeding. Uptake was assessed by measuring blood iodine levels in aerially shot feral pigs. In all, 80% of feral pigs sampled in a non-toxic PIGOUT®-baited area had significantly elevated blood iodine, compared with 52% of sampled feral pigs in a meat-baited area (although slightly different baiting strategies were employed). No age or sex bias was evident in PIGOUT®-consuming feral pigs. No monitored manufactured baits were consumed by non-target species in 500 bait-nights. Attractiveness and target-specificity trials of ground-laid, unfenced PIGOUT® baits compared with reference baits were subsequently undertaken in several regions of eastern Australia. Results showed that PIGOUT® was consumed readily by feral pigs at all sites, and that it offered significant improvement in target specificity when compared with unfenced wheat or meat baits. However, the baits were consumed by small numbers of macropods, birds and possums. Available evidence indicates that the target-specificity of PIGOUT® bait is highest in the rangelands, reducing slightly in temperate areas and subalpine forests, where abundance of small animals is higher.

Measuring the Demographic and Genetic Effects of Pest Control in a Highly Persecuted Feral Pig Population

Abstract Substantial efforts have been made to identify the most effective practices for the control and management of invasive vertebrate pest species, such as the feral pig (Sus scrofa). We investigated the demographics, abundance, and molecular ecology of a persecuted feral pig population that was subjected to control. We then applied methodologies to determine if we could retrospectively quantify any changes in the population structure or dynamics of these pigs. Feral pig demographic and abundance parameters indicated that in this population of feral pigs, there were very few detectable changes between the two aerial culling years. We observed this despite environmental conditions being optimal for control. Genetic results indicated that pigs culled in the latter 2004 cull were genetically identical to those pigs that inhabited the area a year earlier. The genetic population was geographically larger than the sample area. These findings indicate that the recovery in feral pig density witnessed in the controlled area was not a result of reinvasion from a separate, genetically distinct population, but rather, it was the result of reinvasion from feral pigs outside the study area but within the same genetic population. Importantly, we were unable to detect any recent genetic bottlenecks. This approach has considerable potential for auditing the effectiveness of control programs of pest species and assessing the feasibility of impacting upon or locally eradicating many other free-ranging pest species.

Vaccination of feral pigs (Sus scrofa) using iophenoxic acid as a simulated vaccine

OBJECTIVES To develop an encapsulation method for delivery of vaccines to feral pigs, and quantify the effect of iophenoxic acid on captive feral pig blood iodine concentrations to assist in investigation of factors affecting vaccine uptake. DESIGN AND METHODS Feral pigs were administered iophenoxic acid by oral gavage, and consumption was assessed for different encapsulation methods in baits. Blood iodine concentrations were monitored for eight days after consumption. The relationship between dose rate, time since dosing and blood iodine concentration was assessed for gavaged and baited captive feral pigs. Wild feral pigs were baited with PIGOUT baits containing 20 mg of encapsulated iophenoxic acid to simulate a vaccination program. Using knowledge from the pen studies, bait uptake and factors affecting bait uptake were investigated. RESULTS Bait-delivered iophenoxic acid led to variable and inconsistent changes in blood iodine concentrations, in contrast to pigs receiving iophenoxic acid by gavage. This precluded accurate assessment of the quantity consumed, but still allowed a conservative determination of bait uptake. Iophenoxic acid in smaller capsules was consumed readily. Increasing baiting intensity appeared to increase bait uptake by wild feral pigs, and pigs of varying sexes, ages and weights appeared equally likely to consume baits. CONCLUSIONS Encapsulated liquids can be delivered to feral pigs within baits, should the need to vaccinate feral pigs for fertility or disease management arise. High baiting intensities may be required.

Delivering and registering species-tailored oral antifertility products: a review

Technologies that induce infertility in wildlife are advancing rapidly. This is due largely to our increasing understanding of reproductive physiology, as well as the demand for management techniques that reduce fertility rather than increase mortality. However, transferring wildlife fertility control from the laboratory into landscape-scale utility for free-ranging animal populations will be highly dependent on products possessing oral activity and cost-effectiveness. A significant challenge to the delivery process is providing the international regulators in each jurisdiction with the most relevant data packages they need to assess new products. An essential part of any product registration for free-ranging animals will be the development of species-tailored delivery systems, especially so for non-specific antifertility actives. This review examines the current range of orally deliverable antifertility options, broadly classifies them according to overall risk compared with alternative vertebrate pesticides, outlines a species-tailoring process that reduces identified risks, and encompasses the data requirements for their registration for sale in Australasia, the USA and Europe.