Do food protein and carbohydrate content influence the pattern of feeding and the tendency to explore of forest tent caterpillars?

This study examines whether the ratio of protein to carbohydrate affects the timing of meals and the propensity to explore of forest tent caterpillars (Malacosoma disstria). The behavior of fourth instar caterpillars was observed on three semi-defined artificial diets varying in protein (p)-carbohydrate (c) ratio. These diets were (a) p14:c28, (b) p28:c14, and (c) p35:c7. The probability of initiating feeding at first contact with the food and the duration of the first feeding event did not vary across diets, suggesting not much difference in phagostimulatory power. There was also no difference in the total time spent eating, at rest and in motion between diets. However, the timing and duration of meals varied significantly; more short meals were observed on the carbohydrate-biased diet. The duration of pauses between meals also increased with food protein content. Furthermore, caterpillars on the carbohydrate-biased diet were more likely to leave the trail leading to the known food source and to discover a second food source, suggesting that protein deprivation promotes exploration. These findings shed insight into the physiological responses to protein and carbohydrate ingestion and demonstrate how post-ingestive effects can favor consumption of foods containing protein without invoking an explicit mechanism of independent nutrient regulation, but simply by influencing the pattern of feeding and the propensity to explore.     

How does pattern of feeding and rate of nutrient delivery influence conditioned food preferences?

Ruminant herbivores have been shown to learn about food properties by associating food flavours with the food’s post-ingestive consequences. Previous experimentation supporting the conditioned food aversion/preference hypothesis has generally employed very simple diet learning tasks which do not effectively represent the wide range of foods selected within single bouts typical of wild, free-ranging ruminant herbivores. We tested the ability of a ruminant herbivore to associate a food with artificially administered nutrient rewards in a designed experiment where we altered the temporal pattern of encounter with the food as well as the nature (fast or slow reward) of the post-ingestive outcome. Twenty-four goats were offered branches of Sitka spruce (SS) and Norway spruce (NS) for 4 h per day on two days per week for five weeks. The pattern of feeding varied with treatment such that the species on offer changed every hour (short) or every 2 h (long). The energy treatment altered the reward delivered during Sitka consumption so that animals were dosed either with predominantly sugar (rapidly fermented), predominantly starch (slower fermentation rate), or with water (placebo). Preference was measured on the day following each learning day. We expected that goats would find it easier to associate SS with post-ingestive rewards when the duration of encounter was longest, and that associations would be stronger with the most rapidly digested post-ingestive reward. In the event, goats did not alter their consumption of SS in response to the treatments. Our results suggest that at the scale of temporal resolution of encounters with different plant species (1–2 h), and at the different rates of experiencing post-ingestive consequences tested in this experiment, ruminants do not appear to discriminate the nutritive properties of foods predominantly through a post-ingestive feedback mechanism. They must, instead, use a range of cues—including post-ingestive consequences—to assess food properties. An erratum to this article can be found at     

How can the feeding habits of the sand tiger shark influence the success of conservation programs?

The feeding habits of the sand tiger shark Carcharias taurus , one of the most threatened sharks of the world, are poorly known. Sand tiger sharks are critically endangered in the South-west Atlantic. Since 2007, the law requires that all individuals caught in recreational fisheries off Argentina must be released. Using data from a north Patagonian recreational fishery ( n =164 stomachs with contents), we analyzed the diet of sand tiger sharks in relation with size, sex, maturity stage and season; assessed prey consumption patterns and hooking location; and estimated diet overlap with fishery landings. Sand tiger sharks consumed mainly teleosts (55.4% of the total prey number, N ) and elasmobranchs (41.84% N ), and ate more benthic elasmobranchs (batoids and angel sharks) as they become larger. Sharks swallowed prey mostly in one piece (93.7%) and were hooked mainly in internal organs (87.4%, n =175), causing occlusion and perforation of the esophagus and stomach, and lacerations to the pericardium, heart and liver. Sand tiger sharks fed on the most heavily landed species, overlapping almost completely (>90%) with fishery landings. Conservation plans should take into account that releasing hooked sharks could be insufficient to minimize fishing mortality and that competition for food with fisheries is likely to occur.     

New food sources,conservation of biodiversity and sustainable development: can unconventional animal species contribute to feeding the world?

There is increasing interest in the potential of animal species that do not currently fall within the scope of conventional livestock farming to supplement the production of animal protein for human consumption. This paper provides an overview of the current situation and the conditions the led to it, and offers an analysis of the future of wildlife usage within the general framework of sustainable development.     

How does parental role influence the activity and movements of breeding wolves?

We studied the activity and movements of a male and a female wolf during breeding in the Bieszczady Mountains, Poland. The female was less active and mobile and on average closer to the den than the male. The male was less active and mobile when the pack size was seven compared to a year when the pack consisted only of the breeding pair. We conclude that the roles played by breeding males and females rearing pups influence their activity, and that breeding males in larger packs move less during the nursing period because of help by other pack members.     

Edge effects on insect–plant food webs: assessing the influence of geographical orientation and microclimatic conditions

1. Geographical orientation affects the magnitude of microclimatic edge effects, mainly by altering the exposure to solar radiation. There is considerable evidence available concerning the influence of microclimatic edge effects on organisms at the population level, although little is known about effects at the community level, and variations with edge geographical orientation have barely been addressed. The present study investigated the influence of microclimatic conditions at the forest interior and edges with different geographical orientation on plant–leafminer–parasitoid food webs in the fragmented Chaco Serrano forest located in Central Argentina. 2. Microclimatic variables were measured in three locations: interior, north, and south-facing edges of six forest fragments. In each location, plant resource availability was assessed and mined leaves were collected to investigate plant–leafminer–parasitoid communities by rearing leafminer and parasitoid adults. 3. The results obtained revealed changes in the specific composition of plant, leafminer and parasitoid communities among locations, although they failed to detect location influences on most variables linked to abundance (except for leafminers), richness or food web structure. Leafminer abundance was negatively related to temperature, whereas their richness was related, also negatively, to moisture. Instead, parasitoids were favoured by higher temperatures and light levels, stronger winds, and lower humidity. 4. The results of the present study indicate that the effects of microclimatic conditions may depend on the trophic level considered. Moreover, the findings suggest that possible trade-offs between direct and indirect effects (such as plant quality, floral resources, etc.) of microclimatic conditions could influence plant and insect responses to location.     

Does breeding status influence haematology and blood biochemistry of yellow-legged gulls?

We compared the haematological and biochemical values within a population of yellow-legged gulls (Larus michahellis) in the Chafarinas Islands (Northern Africa), in non-breeding (February) and breeding (May) animals. We collected blood samples from 51 adults. We found that according to the haematological data, there was a significant variation in haemoglobin content, and a higher proportion of heterophils, thrombocytes, and Haemoproteus infection in breeding individuals with a lower level in basophils. Blood biochemistry showed a higher level in plasmatic proteins, calcium, phosphorus, thiobarbituric acidreactive substances and alkaline phosphatase as well as alanine aminotransferase activity in breeding animals while cholesterol and phospholipid levels showed a lower level. There was also a sexual difference in triglycerides, albumin, thiobarbituric acid-reactive substances and alkaline phosphatase activity. Hence, the haematological and blood chemistry values of yellow-legged gulls showed some differences between breeding and non-breeding individuals as well as between sexes.     

All you can eat: is food supply unlimited in a colonially breeding bird?

Food availability is generally considered to determine breeding site selection and therefore plays an important role in hypotheses explaining the evolution of colony formation. Hypotheses trying to explain why birds join a colony usually assume that food is not limited, whereas those explaining variation in colony size suggest that food is under constraint. In this study, we investigate the composition and amount of food items not eaten by the nestlings and found in nest burrows of colonially nesting European bee‐eaters (Merops apiaster). We aimed to determine whether this unconsumed food is an indicator of unlimited food supply, the result of mistakes during food transfer between parents and chicks or foraging selectivity of chicks. Therefore, we investigated the amount of dropped food for each nest in relation to reproductive performance and parameters reflecting parental quality. Our data suggest that parents carry more food to the nest than chicks can eat and, hence, food is not limited. This assumption is supported by the facts that there is a positive relationship between dropped food found in a nest and the number of fledglings, nestling age, and chick health condition and that the amount of dropped food is independent of colony size. There is variation in the amount of dropped food within colonies, suggesting that parent foraging efficiency may also be an important determinant. Pairs nesting in the center of a colony performed better than those nesting on the edge, which supports the assumption that quality differences between parents are important as well. However, dropped food cannot be used as an indicator of local food availability as (1) within‐colony variation in dropped food is larger than between colony variation and, (2) the average amount of dropped food is not related to colony size.     

Review: can diet influence the selective advantage of mitochondrial DNA haplotypes?

This review explores the potential for changes in dietary macronutrients to differentially influence mitochondrial bioenergetics and thereby the frequency of mtDNA haplotypes in natural populations. Such dietary modification may be seasonal or result from biogeographic or demographic shifts. Mechanistically, mtDNA haplotypes may influence the activity of the electron transport system (ETS), retrograde signalling to the nuclear genome and affect epigenetic modifications. Thus, differential provisioning by macronutrients may lead to selection through changes in the levels of ATP production, modulation of metabolites (including AMP, reactive oxygen species (ROS) and the NAD⁺/NADH ratio) and potentially complex epigenetic effects. The exquisite complexity of dietary influence on haplotype frequency is further illustrated by the fact that macronutrients may differentially influence the selective advantage of specific mutations in different life-history stages. In Drosophila, complex I mutations may affect larval growth because dietary nutrients are fed through this complex in immaturity. In contrast, the majority of electrons are provided to complex III in adult flies. We conclude the review with a case study that considers specific interactions between diet and complex I of the ETS. Complex I is the first enzyme of the mitochondrial ETS and co-ordinates in the oxidation of NADH and transfer of electrons to ubiquinone. Although the supposition that mtDNA variants may be selected upon by dietary macronutrients could be intuitively consistent to some and counter intuitive to others, it must face a multitude of scientific hurdles before it can be recognized.     

Crystallization of α- and β-carotene in the foregut of Spodoptera larvae feeding on a toxic food plant

In the animal kingdom, carotenoids are usually absorbed from dietary sources and transported to target tissues. Despite their general importance, the uptake mechanism is still poorly understood. Here we report the “red crop” phenomenon, an accumulation of ??- and ??-carotene in crystalline inclusions in the enlarged foregut of the polyphagous Spodoptera larvae feeding on some potentially toxic plant leaves. The carotene crystals give the insect foregut a distinctive orange-red color. The crystals are embedded in a homogenous lawn of the bacterium Enterococcus casseliflavus, but the carotene seems to be selectively taken from the food plant. Caterpillars which fail to develop these carotene crystals exhibit a high mortality or fail to develop to adulthood. The crystallization of carotene and the enlargement of the foregut thus appears to manifest a multiple-step physiological adaptation of the insects to toxic food plants.     

A field study on the influence of food and immune priming on a bumblebee–gut parasite system

Laboratory experiments are often preferred over field experiments because they allow the control of confounding factors that would otherwise influence the causal effect of a particular focal experimental factor. These confounding factors can, however, significantly alter the response of an organism confronted with a particular situation, which can have great implications. In a field experiment with a bumblebee host–parasite system, we looked at the influence of additional food supply and immune challenge on various colony fitness values and parasite traits. We could confirm the importance of food on the colony fitness, but not on parasite infection probability or parasite genetic diversity. In contrast to the findings of laboratory experiments of this system, challenge of the immune system had no significant effect on colony fitness or parasite infections. These results likely reflect an overriding effect of environmental variation without disproving the concept of a cost of defence per se. But the results also demonstrate that confounding factors purposely controlled for in the laboratory have to be weighed against their ecological relevance, and stress the need for careful analysis before any direct transfer is made of laboratory results to field situations.     

Buffering against food availability? The physical environment has little influence on breeding performance of fairy prions (Pachyptila turtur)

The breeding performance of seabirds is constrained by the availability of marine‐based prey, which may be influenced by competition with other seabirds, and environmental conditions. Fairy prion (Pachyptila turtur) populations have declined substantially in New Zealand since the introduction of mammalian predators; remaining small populations provide an opportunity to examine the effect of environmental factors on reproductive success in the absence of competition. Using 11 years of nest monitoring data and eight years of chick measurements we investigated (i) the link between physical environmental factors, breeding success rates and chick fledging size, and (ii) the relationship between chick fledging size and likelihood of natal‐colony recapture. Despite annual variations in the Southern Oscillation Index (SOI) and sea surface temperatures (SST), breeding success and chick fledging weights remained similar throughout the entire period, possibly due to the use of behavioural buffering mechanisms by parents. Fledgling wing lengths differed among years, and were predicted by early winter and early spring values of the SOI and late spring and summer SSTs. In years of high SOI and high SST, fairy prions fledged with longer wings, possibly due to increased availability of the euphausiid Nyctiphanes australis, their main prey. River flows and rainfall were unrelated to breeding success or chick measurements: the influence of freshwater on the marine system at this locality acts at smaller timescales than those studied here. Using the 2004 and 2005 cohorts, there was no link between fledging size and likelihood of recapture, except for the 2005 cohort which had unusually low 6‐year recapture rates, and shorter‐than‐average wing lengths. A combination of low sea temperatures and an El Niño event in 2005 may have led to a reduction in euphausiid availability, ultimately affecting post‐fledging survival.     

The soundscape of Arctic Charr spawning grounds in lotic and lentic environments: can passive acoustic monitoring be used to detect spawning activities?

The aims of this study were to (i) assess the efficacy of passive acoustic monitoring (PAM) for detecting Arctic Charr at their spawning grounds and (ii) characterize the overall acoustic soundscape of these sites. PAM was carried out over three Arctic Charr spawning grounds in the UK, one lotic and two lentic. 24-h cycles of recordings were collected prior to and during the Arctic Charr spawning season, which was determined from data returns by simultaneous net monitoring. Acoustic analysis consisted of manual quantification of sound sources, Acoustic Complexity Index (ACI) calculation and spectral analysis in 1/3 octave band (SPL; dB re 1 μPa). In the lotic spawning ground, prior to the beginning of Arctic Charr spawning, SPL and ACI showed a restricted range of variation throughout the 24-h, while during spawning the night values of SPL and ACI were found to significantly increase, concurrently with the rate of gravel noise induced by fish spawning activities and fish air passage sounds. Both prior to and during the Arctic Charr run, the lentic soundscape was characterized by diel variation due to the daytime presence of anthropogenic noise and the night-time presence of insect calls, while only a few occurrences of fish air passage sounds and gravel noise were recorded. These findings suggest that PAM over Arctic Charr spawning grounds could provide meaningful information to be used in developing management plans for this threatened species, such as determining the location and time of arrival, diel pattern and length of spawning activities.     

Seasonal feeding and fecundity of the calanoid copepod Acartia tonsa in Long Island Sound: is omnivory important to egg production?

Many suspension-feeding copepods show omnivorous feeding behavior. However, the relative contribution to egg production of herbivorous and heterotrophic feeding in copepods remains an open question. In this study, we quantified pigment ingestion rates and egg production rates of the planktonic calanoid copepod Acartia tonsa from July to November of 1986 in Long Island Sound, a large temperate estuary. Pigment ingestion and egg production rates were better correlated to the > 10-µm chlorophyll size fraction than total chlorophyll. Maximum pigment ingestion and egg production rates were observed during the fall bloom in September. Pigment ingestion and egg production rates were linearly related. However, pigment ingestion rates accounted for only 48% of the variance in egg production rates. If female A. tonsa had fed entirely as herbivores over the course of the season, the observed gross efficiency of egg production, K₁ = egg production ratelpigment ingestion rate, in terms of nitrogen, would have been 0.68. This growth efficiency is considerably higher than the expected value, K ₁ = 0.38, for this species based on laboratory studies of herbivorous feeding. We suggest that the ratio H = K ₁/K₁ is a measure of the fraction of egg production that is due to herbivorous feeding. Thus, we infer that herbivory accounted for 56% (0.38/0.68) of egg production in A. tonsa in this study. The ratio H is an useful tool in examining the relative contribution to egg production of herbivorous and heterotrophic feeding in copepods.     

Does a polyphagous caterpillar have the same gut microbiota when feeding on different species of food plants?

We used classical culture techniques to explore gut bacteria and changes associated with dietary change in the highly polyphagous, tropical caterpillar Automeris zugana (Saturniidae). Fifty-five third instar wild-caught sibs feeding on Annona purpurea (Annonaceae) in the Area de Conservación Guanacaste (ACG) in northwestern Costa Rica were divided into eight groups. Each of seven groups was reared to the ultimate instar on another species of food plant normally used by A. zugana. Some pupae were also analyzed for the presence of bacteria. Aerobic bacterial cultures were obtained from all 33 caterpillar guts and the eight pupae inventoried. There was no clear pattern in species composition of cultivated bacteria among the eight diets, and each caterpillar on a given food plant carried only a small fraction of the total set of species isolated from the set of caterpillars feeding on that food plant. Taken as a whole, the larvae and pupae contained 22 species of cultivable bacteria in 12 genera. Enterobacter, present in 81.8% of the samples, was the genus most frequently isolated from the caterpillars, followed by Micrococcus and Bacillus. Bacillus thuringiensis was isolated from 30.3% of the dissected caterpillars, but found in caterpillars feeding on only half of the species of food plants.     

The influence of captive breeding management on founder representation and inbreeding in the ‘Alalā, the Hawaiian crow

The ‘Alalā (Corvus hawaiiensis), or the Hawaiian crow, was historically only found on the island of Hawai‘i, declined greatly in the twentieth century, and was last seen in the wild in 2002. A captive breeding program was initiated in the 1970s and 113 individuals were in captivity in 2014. All of the present day individuals are descended from nine founders. From pedigree analysis, 50 % of the initial ancestry was from a single founder pair and as of 2014, 45 % of the ancestry was still from this pair. Six other founders have also contributed substantially to the population and managed breeding has increased and evened out their contributions in recent years. Managed breeding has also kept the inbreeding level at the relatively low level of 0.120 in 2014. However, for most of the history of the population, all of the inbreeding was from the single founder pair and in 2014, 76 % of the inbreeding was still from this pair. As a result, the high inbreeding depression previously seen in this population appears to descend from this single pair. Breeding management to maximize founder genome equivalents, which takes into account loss of variation from genetic drift, could increase the genetic representation from the founders, particularly if ancestry from the single founder with only one living descendant is increased.