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PubMed2007

Diademed sifakas (Propithecus diadema) use olfaction to forage for the inflorescences of subterranean parasitic plants (Balanophoraceae: Langsdorffia sp., and Cytinaceae: Cytinus sp.).

Primates usually locate food resources using visual cues and memory, yet the potential for olfactory-guided (or olfactory-assisted) food location remains relatively unexplored. Here we report observations of wild Propithecus diadema that strongly suggest that olfaction is used to locate the inflorescences of two subterranean parasitic plant species (Langsdorffia sp. and Cytinus sp.). These valued but seasonal food resources are found obscured in leaf litter, and sifakas spend considerable time on the ground engaged in what appears to be olfactory exploration before they locate the inflorescences. Because they are visually obscured and occur within a substrate that is rarely used by sifakas, accidental discovery of these resources seems unlikely. Individuals may learn to exploit them by watching conspecifics.

Animals↗
PubMed2002

Scale issues in the study of primate foraging: red colobus of Kibale National Park.

Diet data have been used to address a number of theoretical issues. We often calculate the proportion of time spent eating different foods (e.g., fruits, leaves) to place species into dietary categories and contrast morphological or behavioral traits among categories. Yet we have little understanding of how flexible species can be in terms of the plant parts and species consumed. To address this issue, we analyzed data on the diets of red colobus monkeys (Procolobus badius) from Kibale National Park, Uganda, to evaluate temporal and spatial variability in the plant parts and species eaten. After considering observer differences and sampling issues, we evaluated how different a group's diet could be if samples were taken in different years. We found that the diet of the same groups showed significant, consistent changes over a 4-year period. For example, the time spent feeding on leaves increased from 56% in 1994 to 76% in 1998. The plant parts and species eaten by eight groups inhabiting different types of forest (e.g., pristine, logged, riverine) varied among groups. The largest interdemic difference was seen in the use of young leaves (38%). Dietary differences were also found between groups with overlapping home ranges (41-49% overlap). Different subspecies of Procolobus badius also varied in diet; however, this variation was often not of the magnitude documented within Kibale for the same population. The fact that diet can vary considerably over small spatial and short temporal scales within the same species raises the intriguing question as to what level of interspecific difference is biologically significant for addressing particular questions. We conclude that behavioral flexibility blurs our traditional stereotypic assessment of primates; a study of one group that occupies a specific habitat at one point in time may not adequately represent the species.

Animals↗
PubMed2005

Electrospray[+] tandem quadrupole mass spectrometry in the elucidation of ergot alkaloids chromatographed by HPLC: screening of grass or forage samples for novel toxic compounds.

Ergot alkaloids are mycotoxins generated by grass and grain pathogens such as Claviceps, for example. Ergot alkaloid-poisoning syndromes, such as tall fescue toxicosis from endophyte-infected tall fescue grass, are important veterinary problems for cattle, horses, sheep, pigs and chickens, with consequent impact on food, meat and dairy industries. Damage to livestock is of the order of a billion dollars a year in the United States alone. HPLC with UV and fluorescence detection are the predominant means of ergot alkaloid determination, with focus on quantitation of the marker compound ergovaline, although ELISA methods are undergoing investigation. These techniques are excellent for rapid detection, but of poor specificity in defining new or poorly characterized ergot alkaloids and related compounds. This paper demonstrates the facility of using electrospray(+) mass spectrometry with multiple reaction monitoring (MRM) detection during chromatographic examination of ergot alkaloid standards of lysergic acid, lysergol, ergonovine, ergovaline, ergotamine, ergocornine, ergocryptine and ergocrystine by HPLC. Ergoline-8 position epimers could be separated on the gradient HPLC system for ergocornine, ergocrystine and ergonovine and appeared as shoulders for ergotamine and ergovaline; epimers generally showed different patterns of relative intensity for specific MRM transitions. There was reasonable correspondence between retention of standards on the 2-mm ESI(+)MS phenyl-hexyl-based reverse phase column and those on the 4-mm C18-based column. Since up to 10% of clinical cases involving toxin exposure display unidentified chromatographic peaks, 11 samples of feed components associated with such cases were studied with developed MRM methods to attempt elucidation of crucial components if possible. Ergotamine appeared in all, ergovaline appeared in five and ergocornine appeared in six; ergonovine, ergocryptine, ergocrystine and lysergol also appeared in several. In addition, molecular weights of compounds newly revealed by mass spectrometry suggested ergosine, ergostine and ergoptine in four samples, for which standards were not available. Dehydrated products of ergotamine, ergocrystine and ergocornine were discovered, along with dihydrogenated ergocrystine and ergocryptine in seven of the samples, and the issue was raised as to whether dehydration was strictly an instrument-derived artifact. Finally, five of the samples, along with fescue seed standard, evidenced one or more of 14 new ergot alkaloids ranging in size from 381 to 611 molecular weight and with key mass spectral characteristics of ergot alkaloids, specifically the pair of peaks m/z 223 and 208, corresponding to the ergoline ring system and its demethylated variant, respectively. It is anticipated that findings such as these will provide impetus to future development of analytical methodology for these heretofore relatively rare ergot alkaloid species.

Animal Feed↗
PubMed1999

Risk-sensitive foraging: choice behaviour of honeybees in response to variability in volume of reward.

We tested risk sensitivity towards variability in volume of reward with harnessed honeybees, Apis mellifera, in a proboscis-extension conditioning paradigm. We conditioned each subject to turn its head and extend its proboscis towards one of two presented odours; one odour was associated with a constant reward volume and the other with a variable reward volume that was either low or high, with probabilities P=0.75 and (1-P)=0.25, respectively. The volumes of rewards were varied among three experimental conditions. In conditions I and II, the variable reward option included a low reward of zero (i.e. reinforcement was withheld in the low reward value); in condition I, the mean of the variable and of the constant reward options were the same, and in condition II, the variable reward option had a higher mean reward than the constant reward option. The behaviour of subjects did not differ between treatments and the majority of individuals were risk averse. In condition III, the variable reward option did not include a zero reward and the mean reward did not differ between options. Very few of the individuals assigned to condition III developed a preference for either reward option. Thus, honeybees are risk sensitive to variability in volume of reward in some conditions and the degree of risk sensitivity depends on characteristics of the reward distributions. The most salient characteristic may be a relative measure of variability, such as the value of the coefficient of variation of reward. The experimental paradigm that we developed is a powerful tool for studying the mechanism of risk sensitivity in bees, as well as other aspects of learning, decision making, perception and memory. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

Pigs shift too: foraging strategies and spatial memory in the domestic pig.

In a previous experiment, we showed that domestic pigs, Sus scrofa, unlike many other species, performed accurately in a spatial memory task, where visits to a previously baited food trough were rewarded (win-stay). We investigated whether pigs have a predisposition for this strategy, by comparing their performance in a radial arm maze under either win-stay (N=10) or win-shift (N=10) reward contingencies. Contrary to our earlier results, only one of the animals in the win-stay condition was able to reach the imposed criterion level of accuracy. The performances of the other win-stay pigs did not deviate from random. All pigs in the win-shift condition reached criterion by day 25 of the experiment, and performed better than expected by chance. Analysis of the types of errors made matched our a priori predictions that shift movements would occur more frequently, especially within visits to the maze. We suggest that the difference in learning rates may reflect the fact that win-stay pigs needed to use two different rules, stay between trials and shift within trials, while win-shift pigs only needed to use the shift rule. In our previous study, win-stay pigs did not experience a conflict of rules and this may have facilitated stay learning. We found evidence of a recency effect in win-shift animals and a primacy effect in the win-stay group. However, we discuss the unsuitability of these specific terms in this type of experiment, and propose an alternative interpretation of the results. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

Risk-indifferent foraging behaviour in honeybees.

We studied the influence of variance in reward volume on choice behaviour of honeybees, Apis mellifera carnica, by training bees to collect sucrose solution from four newly developed artificial feeders. The feeders were electromechanical devices, each controlled by a microprocessor, which monitored the experiments, controlled reward delivery and stored the data. The parameters that varied between the feeders were the amount and variance of reward. The four feeders were arranged in two pairs, with the two feeders in each pair set to the same reward parameters. Constant feeders offered a fixed amount of sucrose solution at each bee visit; variable feeders offered a normally distributed reward with a standard deviation equal to the mean. We tested three reward combinations under two variance conditions. The bees matched their choice frequencies to the mean amount of reward. This applied both to the constant and the variable feeders. Thus the bees were able to discriminate feeders by the amount of reward and were able to estimate the mean reward for the variable flowers. The proportion of immediate returns to the same feeder increased with the amount of sucrose solution imbibed at each visit, indicating that bees were able to perceive the amount of reward at each visit. However, there was no influence of variance on the choice behaviour of the bees, ruling out the possibility that bees are risk sensitive under these conditions. We discuss risk indifference in choice behaviour of bees in the context of several models of risk sensitivity. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2001

Modelling antipredator vigilance and flight response in group foragers when warning signals are ambiguous.

The trade-off between feeding and vigilance in flocks of birds has been extensively studied and modelled. An assumption of many models is that if one bird spots the predator, it gives a signal and the rest of the flock takes flight. However, it has been observed that birds do not always respond to signals and in fact many signals turn out to be false alarms. Since taking flight is both costly in time and energy, it may be advantageous for birds not to respond to all alarm calls. A model is developed to show under what circumstances birds should respond to a signal. The model predicts that under most, but not all, circumstances, birds should respond to multiple detections but not to single detections. The model also predicts that if birds respond to all flights, they will have to compensate for the time lost to feeding and the greater energy requirement of spending more time in flight, by being less vigilant, and they have a lower probability of survival than birds which only respond to multiple detections.

Animals↗
PubMed2000

Optimal intraguild foraging and population stability.

This article explores effects of adaptive intraguild predation on species coexistence and community structure in three species' food webs. Two Lotka-Volterra models that assume a trade-off between competition and predation strength are considered in detail. The first model does not explicitly model resource dynamics and is considered with both nonadaptive and adaptive intraguild predation; in the latter case predators choose their diet in order to maximize their instantaneous population growth rate. The second model includes resource population dynamics. Effects of adaptive intraguild predation on the community structure along a gradient in environment productivity are analyzed and compared with some experimental results of protist food webs. Conditions under which intraguild predation is adaptive are discussed for both models. It is proved that if intraguild predators are perfect optimizers then intraguild predation should decrease with increasing environmental productivity and adaptive intraguild predation is a stabilizing factor provided environmental productivity is high enough.

Adaptation, Biological↗
PubMed1992

Condensed tannins in some forage legumes: their role in the prevention of ruminant pasture bloat.

For the past 20 years, the focus in our laboratory has been on finding the causes of ruminant pasture bloat and eventually breeding a bloat-safe alfalfa (Medicago sativa L.); i.e., with bloat potential reduced to the economic threshold. In the mid-seventies, the mechanisms of bloat were explored and found to be more physical than chemical. Characteristic of all bloating legumes after ingestion was a very rapid initial rate of ingestion by rumen microbes. Through the study of bloating and non-bloating legumes, factors were elucidated in the plant that would slow this process. One of these factors was the presence of condensed tannins in the herbage. Some of the non-bloating legumes contained these secondary metabolites, but no condensed tannins were found in any of the bloating legumes. Therefore, species containing an appreciable amount of condensed tannins in their leaves and stems are considered to be non-bloating. Conventional breeding methods have not been successful in producing an alfalfa with condensed tannins in its herbage. New approaches using tissue culture techniques are being attempted, but genetic engineering has the greatest potential for success.

Animals↗