Giovanna Massei

Disarmed by domestication? Induced responses to browsing in wild and cultivated olive

Abstract Some theories of plant allocation to defence predict that chemical or structural defences against herbivores should be maximised when browsing is most likely to occur. However, plants are constrained by a trade-off between growth and defence such that slow-growing plants usually have higher levels of secondary compounds, such as phenolics and tannins, than faster-growing ones. Thus, it is possible that the selection for increased yield and growth rate that occurs when plants are domesticated, may cause a reduction in allocation to these compounds. We tested this hypothesis using wild (Olea europaea L. var. sylvestris Brot.) and cultivated (O. europaea L. var. europaea) olive growing in an area with high densities of ungulates. In our study, olives outside fences excluding ungulates were heavily browsed. However, browsing induced an increase in the phenolic content of olives of both varieties in winter but not in spring. In spring, new leaves of both varieties had generally higher levels of phenolics and nitrogen than old leaves, but new leaves in both varieties exposed to browsing had a lower nitrogen content compared to controls. Browsing in both olive varieties caused leaf and shoot density to increase and leaf and shoot length to decrease, but in wild olives browsed shoots lost their leaves and became similar to spines. Structural responses to browsing occurred in spring during regrowth, whilst chemical changes were more obvious in winter, in both varieties. We suggest that olive may exhibit both morphological and chemical responses to browsing, depending on the different resource allocation priorities at different times of year. In spring, independently of browsing, cultivated olive had generally longer shoots and lower levels of phenolics than wild olive. We speculate that domestication may have selected for faster growth, at the expense of allocation to secondary compounds.

Effect of the GnRH vaccine GonaCon on the fertility, physiology and behaviour of wild boar

Fertilitycontrolhasthepotentialtobeusedasanattractivealternativetolethalmethodsforlimitingpopulation growth in overabundant species. This study tested the effectiveness and potential side effects of the single-dose gonadotrophin-releasing hormone (GnRH) vaccine GonaCon on the physiology and behaviour of two groups of captive female wild boar in two sequential trials (Trial 1 and Trial 2). Following vaccination with GonaCon, data on contraceptive effectiveness were recorded as well as data on time budget, social rank, bodyweight, haematology and biochemistry. The concentration of GnRH-antibody titres peaked 2-6 weeks after vaccination and remained relatively high 12 weeks after vaccination. In Trial 1, all control females and none of the treated females gave birth. In Trial 2, faecal progesterone of treated females decreased to basal levels within a month of vaccination. No differences in time budget, social rank and blood parameters were observed between treated and control females. Bodyweight increased more in treated females than in controls. These results indicated that GonaCon can suppress reproduction of wild boar with no significant short-term effects on behaviour and physiology. GonaCon can be regarded as an effective, humane and safe contraceptive for managing wild boar populations.

Chemical and morphological variation of Mediterranean woody evergreen species: Do plants respond to ungulate browsing?

. Plant defense theories suggest that chemical or structural defences should be maximized when and where browsing is most likely to occur. We tested this hypothesis on four evergreen woody species growing in a Mediterranean area with a high density of ungulates. In this system, levels of browsing are more intense in the winter (due to the lack of annual plants) and young foliage is often preferred. Therefore we predicted that the chemical defences of these species, namely their phenolic content, would vary with leaf age, season and damage intensity. In addition, we tested whether ungulates preferentially selected species containing lower phenolic levels, and also whether browsing induced either chemical or morphological changes in damaged plants. Phenolic levels varied greatly between plant species; ungulates browsed preferentially on the species with the lowest phenolic levels. No difference in phenolic content was found between browsed and unbrowsed trees. Morphological changes in heavily browsed trees included an increase in shoot and leaf density and a net decrease in leaf size. We suggest that for Mediterranean plants, which have evolved under high browsing pressure from large mammals, the production of small leaves and dense shoots in response to browsing might decrease ungulate foraging efficiency and hence reduce the rate of further damage as effectively as high levels of chemical defence.

Strength and persistence of conditioned taste aversion in rats: evaluation of 11 potential compounds

Abstract Conditioned taste aversion (CTA) occurs when animals associate the taste of a food with illness and subsequently avoid that food. CTA can be experimentally induced by adding an undetectable, illness-inducing chemical to food. The use of CTA has been suggested as a humane, non-lethal method for vertebrate pest control. The present study tested the ability of the following 11 chemicals to generate CTA in laboratory rats Rattus norvegicus after a single oral administration: thiabendazole, levamisole hydrochloride, xylazine, copper sulphate, caffeine, ipecacuanha, nicotine, aspirin, fluoxetine hydrochloride, clotrimazole and nifedipine. Thiabendazole, levamisole, fluoxetine, and clotrimazole induced strong, long-lasting CTA. No extinction of the aversion was observed over 14 weekly food presentations after an initial administration of thiabendazole. An attenuation of the aversion was noted for rats dosed with levamisole and fluoxetine, although the average food consumption of these groups remained significantly lower than that of controls. Persistence of CTA was negatively related to pre-conditioning food consumption by individual rats.

Iophenoxic Acid as a Long-Term Marker for Wild Boar

Abstract Chemical markers are increasingly used to investigate consumption of baits used to deliver vaccines, toxicants, and contraceptives. We evaluated whether ethyl-iophenoxic acid (Et-IPA) and propyl-iophenoxic acid (Pr-IPA) can be used as long-lasting systemic bait markers for wild boar (Sus scrofa). We presented captive wild boar with baits treated with either Et-IPA or Pr-IPA at 5 mg/kg (low dose), 10 mg/kg (medium dose), and 20 mg/kg (high dose) of body weight. We collected serum from each boar at 5 time points: 5 days, 3 weeks, 6 weeks, 11 weeks, and 39 weeks following ingestion of iophenoxic acid–treated baits. We detected both Et-IPA and Pr-IPA for ≥39 weeks after ingestion. Throughout the trial, the Et-IPA we found in serum was proportional to the amount eaten. At each time point, animals in the high-dose group had significantly more Et-IPA than animals in the low-dose group. We concluded that both compounds can be used as long-lasting markers in wild boar and that Et-IPA can also be employed as quantitative marker to indicate multiple bait uptake. Both compounds have potential applications in the context of vaccination, fertility, and population control campaigns, where baits are used to deliver pharmaceuticals, and in behavioral studies to establish spatial and temporal patterns of bait uptake.

Effects of bait type and deployment strategy on uptake by free-living badgers

Baits are increasingly used in wildlife management to deliver orally administered vaccines and contraceptives. The efficacy and cost-effectiveness of vaccination or fertility-control campaigns can be substantially affected by bait uptake rates. This study assessed whether bait type and deployment strategy affected bait uptake by free-living badgers (Meles meles L.). Six social groups of badgers were presented with three bait types (meat, fruit, cereals) and two deployment strategies (dispersed single baits versus aggregated multiple baits at fixed baiting stations) for six weeks. In each social group, the type of bait and deployment strategy were rotated every week so that by the end of the test every group had experienced all combinations. On three days, biomarkers (ethyl iophenoxic acid, propyl iophenoxic acid and rhodamine B) were added to the baits to determine the proportion of badgers ingesting these baits. The results indicated that both bait type and deployment strategy affected the proportion of baits eaten by badgers and the number of badgers gaining access to baits. Meat and fruit baits were taken significantly more frequently than cereals, and dispersed meat baits had the highest rates of disappearance. Biomarker levels suggested that the proportion of badgers that gained access to all baits was substantially lower when baits were aggregated, although small sample sizes prevented statistical assessment of this effect. The results suggest that dispersed single baits are likely to be consumed in greater proportions by a higher number of individual badgers than multiple baits at fixed stations.

Potential compounds for inducing conditioned taste aversion in ferrets

Abstract Conditioned taste aversion (CTA) develops when an animal associates the taste of a particular food with illness and subsequently avoids consuming that food. We evaluated the potential of two compounds, levamisole hydrochloride and antimony potassium tartrate (APT) to induce CTA to meat in captive ferrets (Mustela furo). On conditioning day, one group of ferrets was presented with meat treated with a compound and another group of ferrets was presented with untreated meat. In post‐conditioning tests we established whether ferrets had acquired an aversion to untreated meat. Ferrets could detect levamisole and formed an aversion to this compound. APT induced an aversion to meat in treated ferrets, which ate less meat than controls. We suggest that APT is a promising agent to induce CTA in ferrets, while levamisole can act as a feeding repellent. The ability of levamisole to induce CTA should be tested once the flavour of this compound is masked.