Harbor porpoise (Phocoena phocoena) reactions to pingers

The use of acoustic alarms (pingers) has been mandated in several gill net fisheries around the world. Even though pingers have shown to reduce the incidental catch there are still questions to be answered in relation to effective range, habituation and displacement. In the present studies, the vocalization behavior of porpoises was recorded in response to two different pingers, AQUAmark100 (20–160 kHz) and AQUAmark300 (10 kHz). The Scottish experiment included an AQUAmark100 pinger running in on/off cycles. The pinger was placed in an array of acoustic click detectors (C‐PODs) spaced at different distances from the pinger. In Denmark, three experiments were conducted. One had the same AQUAmark100 pinger placed in a C‐POD array. The second and third experiment used an AQUAmark300 pinger running in on/off cycles. Both trial results of the AQUAmark100 revealed significant pinger reduction effects at 0, 200, and 400 m distance; however, the vocalization behavior reveal no signs of habituation. The studies of the AQUAmark300 revealed a significant pinger effect at 0 m distance and either none or 17% reduction at 300 m distance. At one station, however, habituation effects were found indicated by an increase in clicks over time. These results are important in relation to pinger use and thus fisheries management.     

Reaction of Harbor Seals to Cruise Ships

Abstract: The largest aggregations of harbor seals (Phoca vitulina) in Alaska, USA, haul out on floating ice in tidewater glacial fjords. Seals use these fjords in peak numbers during the critical periods of pupping, breeding, and molting when visits by tour ships also peak. Documented and suspected declines of harbor seals in fjords with rising vessel traffic underscore the need to better understand possible impacts, particularly in areas where ship visits have risen substantially in the past 2 decades. We examined the interruption of haul-out bouts of harbor seals due to approaching cruise ships in Disenchantment Bay, Alaska. We conducted observations from cruise ships and focused on disturbance of seals as evidenced by seals flushing into the water from the floating ice on which they rested. We investigated rate of flushing in relation to vessel distance, approach angle, group size, and seal type (mother, pup, or other). Using a survival-regression analysis, we found that the risk of disturbing harbor seals increased when ships approached within 500 m; seals approached as close as 100 m were 25 times more likely to enter the water than seals 500 m from a ship. Seals were 4 times more prone to enter the water when ships were approaching directly rather than passing abeam. Seals responded similarly regardless of group size or seal type. Energetic models indicated a potential to disrupt energy balance and cause thermal stress in disturbed pups if they spent >50% of their time in ice-chilled water. Studies at non-glacial sites suggest that pups spend 40–70% of their time in the water. Voluntary guidelines for approaching seals in Alaska recommend that cruise ships approach ≥91 m (100 yards), a distance at which we show 90% of seals would flush into the water. Our findings indicate a need to develop regulations to maintain a 500-m separation between cruise ships and seals in all Alaskan glacial fjords.     

Acoustic monitoring reveals the times and tides of harbor porpoise (Phocoena phocoena) distribution off central Oregon,U.S.A.

Harbor porpoises (Phocoena phocoena) are commonly observed in Oregon's nearshore marine environment yet knowledge of their ecosystem use and behavior remains limited, generating concerns for potential impacts on this species from future coastal development. Passive acoustic monitoring was used to investigate spatial and temporal variations in the presence and foraging activity of harbor porpoises off the Oregon coast from May through October 2014. Digital monitoring devices (DMONs) were deployed to record acoustic data (320 kHz sample rate) in two neighboring but bathymetrically different locations off the Oregon coast: (1) a site on the 30 m isobath in close proximity (<50 m) to a rocky reef, and (2) a site on the 60 m isobath in an open sandy environment. Data were analyzed with respect to two dynamic cyclic variables: diel and tidal phase. Porpoise presence at the rocky reef site was aligned with the ebb phase of the tidal forcing, while, harbor porpoise presence and foraging at the offshore, sandy bottom site was associated with night‐time foraging. The spatial and temporal patterns identified in this study suggest harbor porpoise habitat use is modulated by specific environmental conditions particular to each site that maximize foraging efficiency.     

An economic model of the limits to foraging range in central place foragers with numerical solutions for bumblebees

1. A model is described that evaluates the maximum economic foraging range in central place foragers by using optimality criteria to discriminate between foraging sites at different distances from the forager's central place. 2. The basic model can be varied to suit foragers that optimise either their rate of net energy uptake or their foraging efficiency. 3. The model requires specification of the time and energy budgets of travel and foraging, and of the rewards obtainable at potential foraging sites. 4. The specific case of bumblebees, whose foraging ranges are poorly known, is considered. 5. Numerical solutions of the model for parameter values that represent bumblebees and their forage predict economic foraging ranges exceeding several kilometres. The model demonstrates that economics alone can explain extensive flight ranges in bees.     

Population density of the greater mouse-eared bat (Myotis myotis), local diet composition and availability of foraging habitats

We studied the regional variation in population density of Myotis myotis (Borkhausen 1797) in south-eastern Bavaria, Germany, and its relations to diet composition and the availability of potential foraging habitats. We monitored colony size and juvenile mortality from 1991 to 2003, conducted faecal analyses in 1993 and determined land-use patterns around colonies. The numbers of individuals counted in the nursery colonies showed only small fluctuations over the years. However, data on colony size demonstrated a pronounced regional variation. Epigeic arthropods, mainly Carabidae, were the most important prey. The diet included prey taxa of forest as well as grassland habitats. The percentage of those prey taxa in the diet that originated in grassland managed with different intensity varied according to the availability of these potential foraging habitats around the nursery roosts. The calculated population density of the bats was positively correlated to forest area and especially to the area of mixed forest around the nursery roosts. Our results indicate that the availability of foraging habitats is a limiting factor for local population densities in the greater mouse-eared bat.     

Increasing vulnerability to predation increases preference for the scrounger foraging tactic

When animals forage in groups, individuals can search for foodthemselves (producer tactic) or they can search for and joinother individuals that have located food (scrounger tactic).The scrounger tactic may provide greater antipredator benefitsthan the producer tactic because "scroungers" hop with theirheads up and tend to occupy central positions in a group, whereas"producers" hop with their heads down and tend to occupy edgepositions. We tested whether increasing an individual's vulnerabilityto predation (using wing-loading manipulations) causes an increasedpreference for the scrounger tactic in zebra finches (Taeniopygiaguttata). Wing-loading manipulations were effective at increasingfocal individuals' perception of vulnerability to predation;treatment individuals increased their total time allocated tovigilance, whereas control individuals did not. Treatment individualsalso increased their use of the scrounger tactic (proportionof hops with head up) and scrounged a greater proportion ofpatches, whereas control individuals exhibited no changes. Ourresults are consistent with the hypothesis that the scroungertactic confers greater antipredator benefits than the producertactic, although whether antipredator benefits are achievedthrough differences in head orientation, spatial position, orboth, remains unclear. Our finding that individuals adjust theiruse of the scrounger tactic according to changes in their phenotypeprovides evidence for phenotype-limited allocation strategiesin producer–scrounger games.     

Biomechanics and foraging profitability: an approach to assessing trophic needs and impacts of diving ducks

A biomechanical model of underwater locomotion is described, and data required by the model presented for 3 species of diving duck (Aythya spp.). Based on field observations of behavior and foods consumed, the model is used to estimate energy costs of foraging and minimum food intake rates of canvasbacks (Aythya valisineria) in two habitats in North Carolina. Increased water depth from 0.5 m in Lake Mattamuskeet to 1.5 m in Pamlico Sound increased the net cost of time spent foraging at the bottom by 43%. Biomechanical calculations are combined with data on intake rates at different food densities (Takekawa, 1987) to determine minimum food densities for profitable foraging in Lake Mattamuskeet. Field observations of behavior are used to adjust minimum intake per dive for unsuccessful dives spent locating food patches. Density and dispersion of plant tuber foods in Lake Mattamuskeet, before and after the fall staging period, suggest that the fraction of habitat with tuber densities above a profitability threshold is more critical to canvasbacks than average tuber density. Such factors are important in relating bird energy requirements and benthic sampling data to carrying capacity and total area of usable habitat. The proportion of foods that can be fed upon profitably also determines the fraction of food organisms subject to depletion as components of trophic pathways.     

Application of a novel method for age estimation of a baleen whale and a porpoise

Eyeballs from 121 fin whales (Balaenoptera physalus) and 83 harbor porpoises (Phocoena phocoena) were used for age estimation using the aspartic acid racemization (AAR) technique. The racemization rate (k_Asp) for fin whales was established from 15 fetuses (age 0) and 15 adult whales where age was estimated by reading growth layer groups (GLGs) in the earplugs. The (k_Asp) for harbor porpoises was derived from 15 porpoises (two calves and 13 > 1 yr old) age‐estimated by counting GLGs in the teeth and two calves classified to age based on length. The (k_Asp) values were estimated by regression of GLGs against D/L ratios. For the fin whales an (k_Asp) of 1.15 × 10^?3/yr (SE ± 0.00005) and a D/L ratio at birth [(D/L)₀] of 0.028 (SE ± 0.0012) were estimated, which is in agreement with rates for other mysticeti. For the harbor porpoises a (k_Asp) of 3.10 × 10^?3/yr (SE ± 0.0004) and a (D/L)₀ value of 0.023 (SE ± 0.0018) were estimated, which is considerably higher than found for other cetaceans. Correlation between chosen age estimates from AAR and GLG counts indicated that AAR might be an alternative method for estimating age in marine mammals.     

Foraging in nature: foraging efficiency and attentiveness in caterpillars with different diet breadths

Abstract. 1. Seventy‐seven individual last‐instar caterpillars foraging in the field were examined for 6 h each. They represented four species of Arctiidae of similar size and habitat use. Two, Hypocrisias minima and Pygarctia roseicapitis, are specialists restricted to particular plant genera. The other two, Grammia geneura and Estigmene acrea, are extreme generalists that use many host plant species from multiple plant families. 2. Parameters of behavioural efficiency were monitored. Generalists spent more time walking, rejected more potential host plants, took longer to decide to feed after inspecting a plant, and took relatively more small feeding bouts compared with specialists. 3. This is the first test of differential foraging efficiency in the field in relation to diet breadth of insects and the data indicate that generalists are less efficient in their foraging activities and may suffer from divided attention. The need for attentiveness to enhance efficiency and thereby reduce ecological risk is discussed.     

Sex differences in diet and foraging behavior in white-faced capuchins (Cebus capucinus)

I examined sex differences in diet and foraging behavior in two groups of white-faced capuchin monkeys (Cebus capucinus)in a tropical dry forest at Santa Rosa National Park, Costa Rica. I tested three hypotheses: sex differences in diet and foraging behavior are best explained by (1) sexual dimorphism, (2) the energy demands of pregnancy and lactation for females;and (3) avoidance of competition between the sexes. Sexual dimorphism offered the best explanation of sex differences in the diet and foraging behavior of C. capucinus,accurately predicting that males do more strenuous foraging activity, make less use of small foraging supports, and spend more time on or near the ground. Females spent more time foraging than males did but probably obtained a lower protein yield per unit foraging time. Females exploited more small and embedded invertebrates, while males ate more large invertebrates and vertebrate prey. Pregnant and lactating females spent more time resting and less time foraging than other females did, increasing their foraging return by focusing on foods requiring little handling. There was little evidence of competition avoidance between the sexes.     

Sexual and seasonal variation in the diet and foraging behaviour of a sexually dimorphic carnivore, the honey badger (Mellivora capensis)

The honey badger, or ratel, Mellivora capensis has not been well studied despite its extensive distribution. As part of the first detailed study, visual observations of nine habituated free-living individuals (five females, four males) were used to investigate seasonal, annual and sexual differences in diet and foraging behaviour. Theory predicts that generalist predators 'switch' between alternative prey species depending on which prey species are currently most abundant, and diet breadth expands in response to decreased availability of preferred food types. There were significant seasonal differences in the consumption of eight prey categories related to changes in prey availability but no seasonal differences in food intake per kg of body mass. As predicted, the cold-dry season diet was characterized by low species richness and low foraging yield but high dietary diversity, while the reverse was true in the hot-dry and hot-wet seasons. In accordance with these predictions, results suggest that the honey badger maintains its intake level by food switching and by varying dietary breadth. Despite marked sexual size dimorphism, male and female honey badgers showed no intersexual differences in prey size, digging success, daily food intake per unit body weight or foraging behaviour. Results do not support the hypothesis that size dimorphism is primarily an adaptation to reduce intersexual competition for food.     

State dependence,personality, and plants: light‐foraging decisions in Mimosa pudica (L.)

Plants make foraging decisions that are dependent on ecological conditions, such as resource availability and distribution. Despite the field of plant behavioral ecology gaining momentum, ecologists still know little about what factors impact plant behavior, especially light‐foraging behavior. We made use of the behavioral reaction norm approach to investigate light foraging in a plant species that exhibits rapid movement: Mimosa pudica. We explored how herbivore avoidance behavior in M. pudica (which closes its leaflets temporarily when disturbed) is affected by an individual's energy state and the quality of the current environment and also repeatedly tested the behavior of individuals from two seed sources to determine whether individuals exhibit a “personality” (i.e., behavioral syndrome). We found that when individuals are in a low‐energy state, they adopt a riskier light‐foraging strategy, opening leaflets faster, and not closing leaflets as often in response to a disturbance. However, when plants are in a high‐energy state, they exhibit a plastic light‐foraging strategy dependent on environment quality. Although we found no evidence that individuals exhibit behavioral syndromes, we found that individuals from different seed sources consistently behave differently from each other. Our results suggest that plants are capable of making state‐dependent decisions and that plant decision making is complex, depending on the interplay between internal and external factors.     

The effects of provisioning and crop-raiding on the diet and foraging activities of human-commensal white-faced capuchins (Cebus capucinus)

Non-human primates are coming into increasingly frequent contact with humans and with human-modified environments. The potential for monkeys to survive in such modified landscapes is questionable, and is likely related to a species' behavioral plasticity, particularly as it relates to diet. In this study, I explore the ways in which white-faced capuchins (Cebus capucinus) adjust their diet and foraging behaviors in response to anthropogenic impact. I compare a troop of human-commensal monkeys and a similar troop of wild-feeding monkeys living within the Curú Wildlife Refuge in western Costa Rica for differences in overall diet composition and activity budgets to evaluate the impact of habitat change in this context. The commensal-living white-faced capuchins rely on raided coconut (Cocos nucifera) and oil palm (Elaeis guineensis) crops and provisioned or stolen human foods for over one-half of their total diet. Regardless of this highly anthropogenic diet, the two study troops do not significantly differ in their activity budgets, and the human-commensal troop maintains wild-foraging activities consistent with those of the wild-feeding troop. These data suggest that the white-faced capuchins at this site are responding to anthropogenic disturbance primarily through the exploitation of human food resources, but they do not yet appear to have lost the foraging skills required to survive in this modified landscape on their own. This study adds to our growing body of knowledge on primate survival in matrix habitats, and will hopefully inform primate management plans throughout the Neotropics.     

Effects of increased swimming costs on foraging behavior and efficiency of captive Steller sea lions: Evidence for behavioral plasticity in the recovery phase of dives

A significant component of foraging energetics is the cost of locomotion, which for marine animals, is the cost of swimming. Increases in the cost of swimming may have significant impacts on foraging efficiency. Minimizing the cost of swimming can contribute to the optimization of foraging strategies by reducing the energetic cost of foraging. Results of several field studies suggest that an increase in the cost of locomotion may have comparable effects on foraging behavior and efficiency to a decrease in prey availability. We tested the hypothesis that an increased cost of swimming, brought on by increased hydrodynamic drag, has the same effect on dive behavior and efficiency as reduced prey availability under standard locomotion. Experiments were performed using two adult female Steller sea lions at the Alaska SeaLife Center in Seward, AK, using the same animals and general experimental design previously used to test the effects of reduced prey encounter rate on dive behavior and efficiency. Animals were fitted with a drag-inducing harness for half of the 500 simulated foraging dives in order to increase the cost of swimming. Individual dive duration and foraging time were significantly reduced in all cost-increased dives, comparable to the effects of reduced prey encounter rate. However, on a bout-by-bout basis, dive and foraging efficiency were only slightly reduced, which is likely due to an average 50% reduction in post-dive surface recovery duration during cost-increased dives. Increased heat flux across the body surface measured in a parallel study confirmed a significant increase in work during drag-increased dives. These results suggest that sea lions are able to compensate for changes in the cost of foraging and maintain their foraging efficiency by altering their dive strategy over an entire bout of dives when operating well within their aerobic scope.     

Linking foraging behavior to lifetime reproductive success for an insect parasitoid: adaptation to host distributions

European and American populations of the parasitoid Cotesiaglomerata show pronounced differences in foraging behavior acrossplants and leaves. This variation in spatial aspects of foragingbehavior was observed about 350 generations after the introductionof C. glomerata from Europe to North America. We used a simulationmodel to study how these behavioral differences affect lifetimereproductive success in environments that differ in the spatialdistribution of hosts. The preferred gregarious host Pierisbrassicae occurs in rare large clusters in Europe but is absentin North America. The solitary caterpillars of Pieris rapaeare negative binomially distributed across plants during summerin North America, whereas they are Poisson-distributed in Europe,and early and late in the season in North America. Simulationsshowed that the foraging strategy of American C. glomerata resultedin a higher lifetime reproductive success than did the strategyof European C. glomerata on a Poisson P. rapae distribution,but did not differ on the more clustered negative binomial distribution.American parasitoids spend less time on exploration flights,focusing on the exploitation of P. rapae patches. This suggeststhat C. glomerata has adapted to the North American environmentthrough the loss of exploration traits necessary for the locationof rare clusters of P. brassicae. Lifetime reproductive successof the European strategy was most sensitive to an increase inthe giving up time on infested leaves. This behavioral parameterwas more than twice as high in the American parasitoids comparedwith their European conspecifics.     

Food for thought: linking caloric intake to behavior via sirtuin activity

Sirtuins are thought to form crucial links between energy levels and cellular metabolism. Libert et al. now provide evidence that SIRT1 activity in the brain modifies mammalian emotional behavior via monoamine signaling and that changes in this pathway might contribute to human affective disorders.     

Bridge under troubled water: Turbulence and niche partitioning in fish foraging

The coexistence of competing species relies on niche partitioning. Competitive exclusion is likely inevitable at high niche overlap, but such divide between competitors may be bridged if environmental circumstances displace competitor niches to enhance partitioning. Foraging‐niche dimension can be influenced by environmental characteristics, and if competitors react differently to such conditions, coexistence can be facilitated. We here experimentally approach the partitioning effects of environmental conditions by evaluating the influence of water turbulence on foraging‐niche responses in two competing fish species, Eurasian perch Perca fluviatilis and roach Rutilus rutilus, selecting from planktonic and benthic prey. In the absence of turbulence, both fish species showed high selectivity for benthic chironomid larvae. R. rutilus fed almost exclusively on zoobenthos, whereas P. fluviatilis complemented the benthic diet with zooplankton (mainly copepods). In turbulent water, on the other hand, the foraging‐niche widths of both R. rutilus and P. fluviatilis increased, while their diet overlap simultaneously decreased, caused by 20% of the R. rutilus individuals turning to planktonic (mainly bosminids) prey, and by P. fluviatilis increasing foraging on littoral/benthic food sources. We show that moderate physical disturbance of environments, such as turbulence, can enhance niche partitioning and thereby coexistence of competing foragers. Turbulence affects prey but not fish swimming capacities, with consequences for prey‐specific distributions and encounter rates with fish of different foraging strategies (pause‐travel P. fluviatilis and cruise R. rutilus). Water turbulence and prey community structure should hereby affect competitive interaction strengths among fish species, with consequences for coexistence probability as well as community and system compositions.     

Strategy maps: Generalised giving-up densities for optimal foraging

Finding a common currency for benefits and hazards is a major challenge in optimal foraging theory, often requiring complex computational methods. We present a new analytic approach that builds on the Marginal Value Theorem and giving-up densities while incorporating the nonlinear effect of predation risk. We map the space of all possible environments into strategy regions, each corresponding to a discrete optimal strategy. This provides a generalised quantitative measure of the trade-off between foraging rewards and hazards. This extends a classic optimal diet choice rule-of-thumb to incorporate the hazard of waiting for better resources to appear. We compare the dynamics of optimal decision-making for three foraging life-history strategies: One in which fitness accrues instantly, and two with delays before fitness benefit is accrued. Foragers with delayed-benefit strategies are more sensitive to predation risk than resource quality, as they stand to lose more fitness from a predation event than instant-accrual foragers.     

海切叶蜂的筑巢和访花行为

【目的】研究毛乌素沙地重要野生传粉昆虫海切叶蜂Megachile maritima的筑巢和访花行为对保护其栖息环境具有重要意义。【方法】采用目测及拍照等方法对海切叶蜂的整个筑巢过程进行了连续观测;以2 m×2 m 样方的方式观测海切叶蜂的访花频率、单花停留时间及日活动规律等访花行为,其中日活动规律每天连续观测,共观测7天。【结果】海切叶蜂在沙土中筑巢,每巢只有一个巢室,其筑巢过程为：寻找合适的筑巢地点,挖巢,构建巢室,采集蜂粮,产卵,封住巢室,筑完一个巢。它连续筑完一个巢大约需要9 h。海切叶蜂构建一个巢室需要切取26～29片叶子,为每巢室采集蜂粮11～12次,每巢室内产卵1粒;在塔落岩黄芪和细叶益母草上的平均访花频率分别为（13.23±6.49）朵/min和（16.72±4.84）朵/min,平均单花停留时间分别为（3.08±2.48）s和（2.49±1.31）s。晴天,海切叶蜂在12:00～14:00期间活动较活跃。【结论】海切叶蜂不同个体之间的筑巢行为相似。该蜂在塔落岩黄芪和细叶益母草上的访花过程、访花频率及单花停留时间具有显著的差异。