Foraging Rate Research Articles

Effect of dietary phosphorus concentration and phytate-phosphorus on environmentally-relevant phosphorus excretion in horses

Effect of dietary phosphorus concentration and phytate-phosphorus on environmentally-relevant phosphorus excretion in horses

The effect of hay net design on rate and amount of forage consumed by adult horses

The effect of hay net design on rate and amount of forage consumed by adult horses

Individual energetic state can prevail over social regulation of foraging in honeybees

The energetic state of an individual is a fundamental driver of its behavior. However, an individual in a eusocial group such as the honeybees is subject to the influence of both the individual and the colony energetic states. As these two states are normally coupled, it has led to the predominant view that behaviors, such as foraging, are dictated by the colony state acting through social regulatory mechanisms. Uncoupling the energetic state of an individual honeybee from its colony by feeding it with a non-nutritious sugar, we show that energetically stressed bees in a colony with full food stores do not consume this food to meet their energetic shortfall but instead compensate by first reducing their activity level and then by increasing their foraging rate. This suggests that foraging in eusocial groups is still partly under the regulatory control of the energetic state of the individual and supports the notion that regulatory mechanisms in solitary insects have been co-opted to drive altruistic behavior in eusocial insects. The observation that energetically stressed bees also experience higher mortality during foraging also suggests that energetic stress mediated by a variety of factors can be a common mechanism that underlies the recent observation of bees disappearing from their colonies. We also discuss how nutritional imbalance in a social insect individual can alter its behavior to influence colony life history.

Effects of life phase and schooling patterns on the foraging behaviour of coral‐reef fishes from the genus Haemulon

During this study (December 2009 to December 2010), underwater visual surveys using the focal animal method were performed in the coastal reefs of Tamandaré, north-eastern Brazil. The aim was to analyse the effects of the life phase (juvenile and adult) and schooling patterns (school and solitary) on the feeding behaviour (foraging rates and substratum preferences) of four species of the genus Haemulon (Haemulon aurolineatum, Haemulon parra, Haemulon plumieri and Haemulon squamipinna). PERMANOVA analysis (P < 0·05) indicated that ontogenetic changes and schooling patterns directly influence foraging behaviour. Schooling individuals had low foraging rates (mean ± s.d. = 2·3 ± 2·1 bites 10 min(-1)) and mobility, usually remaining near the bottom; however, solitary fishes had high foraging rates (mean ± s.d. = 12·5 ± 4·6 bites 10 min(-1)). Juveniles preferred feeding in the water column (75% of the total number of bites), whereas adults foraged mainly in sand (80%) and bare rock (20%). All four Haemulon species displayed similar patterns of feeding behaviour as well as preferences for foraging sites and display competition for food resources. In contrast, little is known about their habitat use and foraging behaviour over the diel cycle, particularly the newly settled and early juvenile stages.

The energetic and survival costs of growth in free-ranging chipmunks

The growth/survival trade-off is a fundamental aspect of life-history evolution that is often explained by the direct energetic requirement for growth that cannot be allocated into maintenance. However, there is currently no empirical consensus on whether fast-growing individuals have higher resting metabolic rates at thermoneutrality (RMRt) than slow growers. Moreover, the link between growth rate and daily energy expenditure (DEE) has never been tested in a wild endotherm. We assessed the energetic and survival costs of growth in juvenile eastern chipmunks (Tamias striatus) during a year of low food abundance by quantifying post-emergent growth rate (n = 88), RMRt (n = 66), DEE (n = 20), and overwinter survival. Both RMRt and DEE were significantly and positively related to growth rate. The effect size was stronger for DEE than RMRt, suggesting that the energy cost of growth in wild animals is more likely to be related to the maintenance of a higher foraging rate (included in DEE) than to tissue accretion (included in RMRt). Fast growers were significantly less likely to survive the following winter compared to slow growers. Juveniles with high or low RMRt were less likely to survive winter than juveniles with intermediate RMRt. In contrast, DEE was unrelated to survival. In addition, botfly parasitism simultaneously decreased growth rate and survival, suggesting that the energetic budget of juveniles was restricted by the simultaneous costs of growth and parasitism. Although the biology of the species (seed-storing hibernator) and the context of our study (constraining environmental conditions) were ideally combined to reveal a direct relationship between current use of energy and future availability, it remains unclear whether the energetic cost of growth was directly responsible for reduced survival.

EFFECT OF NITROGEN FERTILIZATION ON GROWTH CHARCTERESTIC AND HAY YILD OF BARLEY VARITES

A Field experiment was carried out in the growing seasons (2009-2010) and (2010-2011) at the experimental Station of College of Agriculture and Forestry, Mosul University, to study the effect of Nitrogen Fertilizer Levels, zero, 80 and 120 Kg N/ha as one dose and split applications on growth characteristics and Hay yield of Barley Cultivars namely; Fourat, Zanbaga , Aswed Arbai and two-rowed local black’.The experiment was applied by Using Split –Plot in Randomized Completely Block Design with three replicates. Nitrogen Fertilization have no clear effect on growth characters and hay yield in the first growing season due to the low rainfall and its irregular distribution, this was true for the one dose and split application of the fertilizer, with positive and negative response, while in the second season the Fertilizer levels were positively affected on flag leaf area, relative growth rate, fresh and dry yield of forage, which their valule at the Fertilizer level 80 Kg N/ha as one dose was superior over their values at control treatment by 26%, 3.6%, 27.9% and 33.3% respectively. Splitting Nitrogen level 80Kg N/ha caused increase in relative growth rate in the First season , and increase flag leaf area, fresh and dry forage yield in the second season. While splitting Fertilizer level 120 Kg N/ha increased the flag leaf area, fresh and dry forage yield in both growing seasons. In the first growing season, the local black variety was superior in all growth characters and hay yield with the exception of Flag leaf area, while in the second growing season the variety Zanbaga was surpassed over other varieties in most growth characters and hay yield

Density-Dependent Habitat Selection in a Growing Threespine Stickleback Population

Human-induced eutrophication has increased offspring production in a population of threespine sticklebackGasterosteus aculeatusin the Baltic Sea. Here, we experimentally investigated the effects of an increased density of juveniles on behaviours that influence survival and dispersal, and, hence, population growth—habitat choice, risk taking, and foraging rate. Juveniles were allowed to choose between two habitats that differed in structural complexity, in the absence and presence of predators and conspecific juveniles. In the absence of predators or conspecifics, juveniles preferred the more complex habitat. The preference was further enhanced in the presence of a natural predator, a perchPerca fluviatilis(behind a transparent Plexiglas wall). However, an increased density of conspecifics relaxed the predator-enhanced preference for the complex habitat and increased the use of the open, more predator-exposed habitat. Foraging rate was reduced under increased perceived predation risk. These results suggest that density-dependent behaviours can cause individuals to choose suboptimal habitats where predation risk is high and foraging rate low. This could contribute to the regulation of population growth in eutrophicated areas where offspring production is high.

Persistent bimodal activity patterns in wild and captive black-tailed godwit Limosa limosa under different environmental conditions

There is a large literature dealing with daily foraging routines of wild birds during the non-breeding season. While different laboratory studies have showed that some bird activity patterns are a persistent property of the circadian system, most of field studies preclude the potential role of an endogenous circadian rhythm in controlling bird’s foraging routines. In this study we compared the patterns of diurnal foraging activity and intake rates of migrating black-tailed godwits, Limosa limosa (radio-tagged and non-tagged individuals) at two stopover sites (habitats) with different environmental characteristics, aiming at identifying proximate factors of bird activity routines. To gain insights into the role of food availability in control of such foraging routines, we also estimated foraging activity patterns in captive godwits subjected to constant food availability. Captive and wild black-tailed godwits showed a persistent bimodal activity pattern through daylight period. Food availability had a significant effect on the intake rates, but had a subtler effect on foraging and intake rate rhythms. Temperature and wind speed (combined in a weather index) showed non-significant effects on both rhythms. Although we could not discard a role for natural diurnal changes in light intensity, an important timing cue, our findings support the idea that an endogenous circadian rhythm could be an important proximate factor regulating foraging activity and food items taken per unit time of wild black-tailed godwits during migration.

An Analysis of Eco-efficiency Scenarios in Dairy Farming: Simulations of Milk Production

Farming eco-efficiency requires the approach of economic efficiency, as well as the impact upon the environment. The analysis of eco-economic efficiency of a dairy farm was done by simulating different levels of milk production. The study starts from the real situation of a farm in which the crops and forage basis, productions, rations, the cost and income were quantified and the nutrient balances P, N and K, as well as the profit value were calculated. By simulating with ±25% the peak milk production, 4 scenarios were enacted with the use of the N-CyCLE software: the minimization of P, N and K balances, respectively the profit maximization. The increase of milk production correlates positively with the profit (r=+0.935 on p<0.001) and also with the nitrogen balance (r=+0.471 on p<0.05). The four scenarios significantly influence the value of profit - the scenario towards maximizing the gross margin generates the highest profit (896.5 euro/cow), and the scenario towards nitrogen minimum balance generates the lowest profit (503.08 euro/cow). The eco- economic character of the farm was obtained using barycentric coordinates of ½ weights from the values of N's scenario at the gross margin rates with the computer algebra software Maple13. The optimization of milk production through gross margin maximization and the nitrogen minimization allows expressing the eco-economic character; in this case, at a peak production of 40 kg/day, the farm acquires an eco-economic character when the nitrogen balance is 91.5 kg N/ha/year and the profit is 769 euro/cow.

Modeling foraging behavior of piping plovers to evaluate habitat restoration success

AbstractHabitat restoration projects are often deemed successful based on the presence of the target species within the habitat; however, in some cases the restored habitat acts as an ecological trap and does not help to improve the reproductive success of the target species. Understanding wildlife–habitat relationships through precise measurements of animal behavior can identify critical resources that contribute to high quality habitat and improve habitat restoration practice. We evaluated the success of a restored piping plover (Charadrius melodus) breeding habitat in New Jersey, USA. We identified the major factors influencing foraging rates, compared foraging activity budgets over 3 yr at restored and natural habitats, and explored the potential of artificial tidal ponds as a viable restoration alternative. Adult foraging rates were higher in artificial pond and ephemeral pool habitats, during low tide, and after breeding activity ended. Adult foraging rates were impeded by the presence of people and vehicles within 50 m. Chick foraging rates were highest at artificial ponds and bay shores and lowest in dunes and on sand flats. Chick foraging rates were strongly hindered by the presence of corvids and the number of people within 50 m. In addition, at artificial tidal ponds, piping plovers spent more time foraging and less time engaged in defensive behaviors (vigilance, crouching, and fleeing) compared to other potential habitats. Our findings support the hypothesis that artificial tidal ponds are a valuable, perhaps superior, foraging habitat. Future beach restoration projects should include this feature to maximize habitat quality and restoration success. © 2011 The Wildlife Society.

Foraging Behavior and Coexistence of Two Sunbird Species in a Kenyan Woodland

We investigated the mechanism of coexistence of the rare Amani Sunbird (Hedydipna pallidigastra) and the widespread Collared Sunbird (H. collaris), within Brachystegia woodland in the Arabuko-Sokoke Forest, Kenya. We compared how prey abundance and search strategies affect resource exploitation by the two species. We used foraging theory to direct our measures of feeding activities as influenced by sunbird species, tree species and foraging height. We evaluated invertebrate abundance among tree species at different heights within trees. The Collared Sunbird primarily used the understory, and the Amani Sunbird primarily used the upper-canopy. Overall, the rate of prey attacks per flight of the Amani Sunbird was 2.8 times greater than that of the Collared Sunbird. The Amani Sunbird, however, used increased search and attack rates in the understory compared with the mid- and upper-canopies, but the Collared Sunbird foraged similarly throughout all strata. We hypothesize that the increased foraging rate of the Amani in the understory reflects increased foraging costs due to interference from the Collared Sunbird in that stratum. Furthermore, the Collared Sunbird exploits rich patches by moving frequently from place to place. The Amani Sunbird forages slowly, with reduced travel rates, and with a greater number of prey captures within a patch. Arthropod density did not differ among the vegetative strata, but was higher in Brachystegia spiciformis and Hymenaea verrucosa than in six other tree species. We hypothesize that the Amani Sunbird appears dependent upon continued tall B. spiciformis trees within the canopy of the Arabuko-Sokoke Forest.

The effect of familiarity on vigilance behaviour in grey squirrels

&#x0D; &#x0D; &#x0D; Introduction: Vigilance enables an animal to obtain information about the environment but often at a cost of reduced foraging rate. some environmental information may not change rapidly, so vigilance might be safely reduced with familiarity with an area. studies have noted this declinein vigilance with familiarity, but the reason for this decline has not been tested. Methods: I proposed and tested two hypotheses to explain this decline in vigilance. The safe experience hypothesis suggests the probability of a predator being nearby but undetected decreases with time spent in an area, enabling an animal to decrease its vigilance due to the reduced risk. The Visual experience hypothesis suggests that as time progresses vigilant animals acquire more information from their surroundings (e.g. refuge locations) allowing for a decrease in vigilance because an animal would not need to detect a predator as early if reaching a refuge required less time. grey squirrels (Sciurus carolinensis) were used to test these hypotheses by feeding them peanut butter in an apparatus that limited their access to visual information by varying degrees. results: An effect of familiarity was evident by a sharp decline in vigilance rates within trials. squirrels adjusted vigilance postures to the different treatments, but the rate of decline in vigilance was unaffected by treatment. discussion: while vigilance is related to visual information, the decline in vigilance with familiarity is not related to the amount of visual information obtained from the environment, giving provisional support to the safe experience hypothesis.&#x0D; &#x0D; &#x0D;

An Analysis of Eco-efficiency Scenarios in Dairy Farming: Simulations of Milk Production

Farming eco-efficiency requires the approach of economic efficiency, as well as the impact upon the environment. The analysis of eco-economic efficiency of a dairy farm was done by simulating different levels of milk production. The study starts from the real situation of a farm in which the crops and forage basis, productions, rations, the cost and income were quantified and the nutrient balances P, N and K, as well as the profit value were calculated. By simulating with ±25% the peak milk production, 4 scenarios were enacted with the use of the N-CyCLE software: the minimization of P, N and K balances, respectively the profit maximization. The increase of milk production correlates positively with the profit (r=+0.935 on p<0.001) and also with the nitrogen balance (r=+0.471 on p<0.05). The four scenarios significantly influence the value of profit – the scenario towards maximizing the gross margin generates the highest profit (896.5 euro/cow), and the scenario towards nitrogen minimum balance generates the lowest profit (503.08 euro/cow). The ecoeconomic character of the farm was obtained using barycentric coordinates of ½ weights from the values of N’s scenario at the gross margin rates with the computer algebra software Maple13. The optimization of milk production through gross margin maximization and the nitrogen minimization allows expressing the eco-economic character; in this case, at a peak production of 40 kg/day, the farm acquires an eco-economic character when the nitrogen balance is 91.5 kg N/ha/year and the profit is 769 euro/cow.

Acute and chronic increases in predation risk affect the territorial behaviour of juvenile Atlantic salmon in the wild

Optimality models predict that territory size will decrease as the costs of defence increase. One poorly understood cost is predation risk, especially the relative influence of short- versus long-term increases in predation risk. Under natural conditions, we quantified the territorial behaviour of juvenile Atlantic salmon, Salmo salar, exposed to either acute or chronic increases in perceived predation risk. The effects of an acute increase in predation risk were assessed by exposing 18 young-of-the-year (YOY) Atlantic salmon to a control of stream water and to an alarm cue (i.e. conspecific skin extract) while monitoring their territorial behaviour. We investigated the effects of a chronic increase in perceived predation risk by quantifying the territorial behaviour of YOY salmon in control versus risky sections of seven sites, where we manipulated the perceived predation risk over a 4-week period by releasing stream water in control sections and alarm cue in risky sections. We found that salmon exposed to the alarm cue decreased the number of switches between foraging stations, but they did not change their territory size or foraging rate. As predicted, YOY salmon in risky sections had smaller territories than in control sections. However, their foraging rates and number of switches between foraging stations did not differ between treatments. Our study suggests that juvenile Atlantic salmon are sensitive to both acute and chronic increases in perceived predation risk under natural conditions, and support the predictions of optimality models that territory size decreases with increasing predation risk.

The effect of high grain versus all forage rations on plasma ghrelin level in sheep

Ghrelin, produced mainly in abomasum of ruminants, is a peptide with roles in the regulation of feeding. The present study assessed the alterations of plasma ghrelin in sheep fed with all forage or high-grain rations and the probable effects of altered ghrelin secretion on feed intake in animals with acidic rumen. Eight Karakul male lambs were divided into the control (n = 4) and experiment groups (n = 4) and fed individually for 20 days. The control group was fed an all forage ration for the whole study period. For the experiment group, 40% of the ration was substituted with ground barley for 10 days. For the rest of the study, 62.5% of the ration was substituted with ground barley. Signs of negative alteration of digestive functions (e.g., reduced feed intake, loose manure with reduced dry matter) were observed in the experiment group after day 10 of the experiment when ground barley was increased to 62.5% of the ration. On days 8 and 10 of each step, blood samples were collected for measuring plasma ghrelin level from jugular vein 1 hour before, and 1 and 3 hours after feeding. In the control group, plasma ghrelin increased 1 hour post-feeding (p < 0.05 in step 1) and decreased 3 hours post-feeding. In the experiment group, however, non-significant decreases were noticed in plasma ghrelin concentration 1 hour after feeding, followed by a sharp and significant rise 3 hours post-feeding (p < 0.05). Comparing the control and the experiment groups, we found that plasma ghrelin concentration was lower in the experiment group 1 hour post-feeding with significant difference (P = 0.002) in the second step. At 3 hours post-feeding, plasma ghrelin was higher in the experiment group with significant difference (P = 0.050) in the second step. In conclusion, ration composition may affect ghrelin secretion in sheep. High-grain rations and acidic condition of the rumen may increase ghrelin secretion within a few hours of feeding. This increase in ghrelin secretion, however, may not result in increased feed intake.

Performance of dairy cows fed rations produced with sugarcane silages treated with additives or fresh sugarcane

An experiment was performed aiming at evaluating the performance of dairy cows fed sugarcane silages treated with additives compared to cows fed fresh forage. Twenty-four Holstein cows were grouped in blocks of three cows, according to parity order and milk production level, in multiple 3 x 3 Latin Square design to evaluate three types of ration (63% roughage and 37% concentrate in dry matter - DM): ration with silage treated with urea (5.0 g/kg of fresh forage - FF) + sodium benzoate (0.5 g/kg FF); ration with silage inoculated with Lactobacillus buchneri (5 x 10(4) cfu/g FF); ration with fresh sugarcane. Each evaluation period consisted of two weeks for adaptation and one week for data collection. Cows fed rations with silages treated with urea + benzoate and L. buchneri showed lower DM intake (18.5 vs 21.4 kg/day) and lower milk production (17.4 vs 18.6 kg/day) in comparison to those fed fresh forage ration. Fat content was higher in the milk of cows fed silage inoculated with L. buchneri compared to cows in the fresh forage group resulting in similar 3.5% fat corrected milk (FCM) among cows in both groups. Cows fed ration with silage treated with urea + benzoate presented intermediate fat content in milk but inferior FCM production compared to animals fed fresh sugarcane. Feed efficiency (kg FCM/kg DMI) was higher for cows fed ration produced with the inoculated silage (0.95), intermediate for cows that received silage treated with the combination of chemical additives (0.91) and lower for cows fed the ration with fresh sugarcane (0.83).

Variation of foraging rate and wing loading, but not resting metabolic rate scaling, of insect pollinators

Morphological, physiological and behavioural variation with body size (i.e. scaling) may affect costs of living in a particular environment for insects and, ultimately, pollination or foraging success. However, few studies have directly assessed the scaling of these traits at the species level. Using two similar-sized pollinator species (the hawkmoth Macroglossum trochilus and the fly Moegistorhynchus longirostrus), we compare intraspecific scaling relationships of resting metabolic rate (RMR), foraging rate (FR) and wing loading (WL) to address this paucity of data. Scaling of RMR was similar for both taxa although the intercepts for the relationships differed. However, these two species showed variation in WL scaling relationships and fundamentally different FR scaling. For M. longirostrus, FR scaling was positive but non-significantly related to body mass while for M. trochilus FR scaling was negative. This suggests that variation in FR and WL, but not RMR scaling, among these flies and hawkmoths may impose significant energetic costs which could affect animal-plant interactions in the wild.

The impact of giant panda foraging on bamboo dynamics in an isolated environment

Wildlife species are threatened by massive habitat destruction worldwide. Habitat fragmentation and isolation spatially constrain animals and in turn cause non-sustainable rates of animal foraging on plant populations. However, little empirical research has been done in large controlled settings to investigate foraging impacts. We conducted an experiment to characterize the impact of panda foraging on the sustainability of its food resource, bamboo, in an enclosed area of natural habitat (approximately 19 ha). We monitored bamboo density, age, and percent cover throughout the enclosure across a 3-year period. We documented marked declines in bamboo density and percent cover as a result of panda foraging, particularly in younger bamboo age classes. We constructed simultaneous autoregressive models to explain bamboo loss to panda foraging and subsequent bamboo recovery as a function of habitat conditions. Areas with high initial bamboo cover not only were prone to high rates of bamboo percent cover loss but also experienced high rates of subsequent bamboo recovery, as bamboo cover loss opened up the understory for new growth. Variograms of ordinary least squares model residuals revealed that the range of spatial autocorrelation in bamboo loss increased over time as available bamboo forage declined. The results have implications for understanding the impact of animal foraging on vegetation and also highlight the importance of preventing further habitat fragmentation and isolation.

Interactions between rate processes with different timescales explain counterintuitive foraging patterns of arctic wintering eiders.

To maximize fitness, animals must respond to a variety of processes that operate at different rates or timescales. Appropriate decisions could therefore involve complex interactions among these processes. For example, eiders wintering in the arctic sea ice must consider locomotion and physiology of diving for benthic invertebrates, digestive processing rate and a nonlinear decrease in profitability of diving as currents increase over the tidal cycle. Using a multi-scale dynamic modelling approach and continuous field observations of individuals, we demonstrate that the strategy that maximizes long-term energy gain involves resting during the most profitable foraging period (slack currents). These counterintuitive foraging patterns are an adaptive trade-off between multiple overlapping rate processes and cannot be explained by classical rate-maximizing optimization theory, which only considers a single timescale and predicts a constant rate of foraging. By reducing foraging and instead digesting during slack currents, eiders structure their activity in order to maximize long-term energetic gain over an entire tide cycle. This study reveals how counterintuitive patterns and a complex functional response can result from a simple trade-off among several overlapping rate processes, emphasizing the necessity of a multi-scale approach for understanding adaptive routines in the wild and evaluating mechanisms in ecological time series.

Foraging Rates of Larval Dragonfly Colonists Are Positively Related to Habitat Isolation: Results from a Landscape‐Level Experiment

There is increasing evidence of intraspecific variation in dispersal behavior. Individual differences in dispersal behavior may be correlated with other traits that determine the impact individuals have on patches they colonize. We established habitat patches-artificial pools-across a landscape, and these pools were naturally colonized by dragonfly larvae. Larvae were collected from pools at different levels of isolation and held under common lab conditions for 5 months. We then compared larval foraging rates. Foraging rate was positively related to habitat isolation, and colonists from the most isolated artificial pools had significantly higher foraging rates than individuals from the least isolated pools. Our results indicate that spatial patterns in colonist behavior can develop across a landscape independent of species-level dispersal limitation. This finding suggests that studies of community structure across space should include an assessment of the distribution of phenotypes as well as species-level dispersal limitation patterns.