Active Hunter Research Articles

Integrative paleophysiology of the metriorhynchoid Pelagosaurus typus (Pseudosuchia, Thalattosuchia).

Paleophysiology is an emergent discipline. Organismic (integrative) approaches seem more appropriate than studies focusing on the variation of specific features because traits are tightly related in actual organisms. Here, we used such an organismic approach (including lifestyle, thermometabolism, and hunting behavior) to understand the paleobiology of the lower Jurassic (Toarcian) thalattosuchian metriorhynchoid Pelagosaurus typus. First, we show that the lifestyle (aquatic, amphibious, terrestrial) has an effect on the femoral compactness profiles in amniotes. The profile of Pelagosaurus indicates that it was amphibious, with a foraging activity in shallow marine environments (as suggested by the presence of salt glands) and thermoregulatory basking behavior in land (as suggested by the presence of osteoderms with highly developed ornamentation). As for the thermometabolism, we show that the mass-independent resting metabolic rate of Pelagosaurus is relatively high compared to the sample of extant ectothermic amniotes, but analysis of vascular canal diameter and inferences of red blood cell size refute the hypothesis suggesting incipient endothermy. Finally, the foraging behavior was inferred using two proxies. Pelagosaurus had a mass-independent maximum metabolic rate and an aerobic scope higher than those measured in the almost motionless Iguana iguana, similar to those measured in the sit-and-wait predator Crocodylus porosus but lower than those quantified in the active hunter Varanus gouldii. These results suggest that Pelagosaurus may have had a hunting behavior involving a slow sustained swimming or a patient waiting in shallow waters, and may have caught preys like gharials, using fast sideways sweeping motions of the head.

Venom-gland transcriptomics and venom proteomics of the Tibellus oblongus spider

The Tibellus oblongus spider is an active hunter that does not spin webs and remains highly underinvestigated in terms of the venom composition. Here, we describe venom glands transcriptome and venom proteome analysis for unveiling the polypeptide composition of Tibellus oblongus spider venom. The resulting EST database includes 1733 records, including 1263 nucleotide sequences with ORFs, of these 942 have been identified as toxin-coding. The database of peptide sequences was built based on of the transcriptomics results. It contains 217 new toxins, 212 of them were detected in the T. oblongus venom by the proteomics.

Risk communication and perceptions about lead ammunition and Inuit health in Nunavik, Canada

ABSTRACT Lead ammunition is commonly used to hunt waterfowl and other wildlife in the Arctic. Hunting with lead is problematic because the toxicant can be transferred to the consumer. Therefore, it is critical to evaluate perceptions and awareness of the risks associated with using lead ammunition among Arctic populations. Results of the Nunavik Child Development Study (a longitudinal health study gathering information on health and well-being among Inuit in Nunavik, Canada) included advice to eliminate the use of lead ammunition in hunting practices. We surveyed 112 Nunavik residents (93 women; 18 men) about their awareness of lead related messages, use of lead ammunition and risk perceptions about contaminants. Sixty-seven participants (59.8%) reported there was an active hunter in their household. We found that only 27% of participants had heard or seen the messages about reducing lead ammunition. After participants viewed the Nunavik Child Development Study messages about lead, 44% stated they would stop using lead ammunition. However, 28% indicated that they would continue using lead ammunition. We conclude that, while messages had an overall positive effect, further study is required to understand why people continue to use lead ammunition.

Qingbo, a common cyprinid fish, responds diversely in behavior and locomotion to predators with different hunting modes.

Almost all prey live in habitats with predators with different hunting modes; however, most studies on predation have investigated the effects of only one predator at a time. In this study, we aimed to investigate whether qingbo (Spinibarbus sinensis), a common cyprinid fish, responds differently to active hunting and ambush predators and how qingbo responds when both types of predators coexist. Juvenile qingbo were subjected to catfish (Clarias fuscus, active hunter) exposure, snakehead fish (Channa argus, ambush hunter) exposure, or mixed predator exposure (catfish and snakehead coexistence) for a duration of 60days. Then, their growth, behaviors, swimming performance, and metabolism were measured. Qingbo subjected to active hunting predator exposure exhibited decreased activity and predator inspection and improved fast-start escape performance compared to those in the control group. However, none of the parameters of the fish subjected to ambush predator exposure changed significantly. Fish subjected to mixed predator exposure exhibited improved fast-start escape performance but increased maintenance energy expenditure, whereas no changes were observed in any of the behavioral variables. Qingbo showed a stronger anti-predator response to active hunting predators than to ambush predators, suggesting that the fish exhibit a stronger anti-predator response to a current direct threat than to a potential threat (a predator exists nearby but seldom presents in attack behavior). Additionally, the response of prey fish to multiple predators was quite complex, and the coexistence and interaction of multiple predator species with different hunting modes may lead to serious stress responses and confound the prey's behavioral responses to each predator.

Reptiles on the wrong track? Moving beyond traditional estimators with dynamic Brownian Bridge Movement Models

BackgroundAnimal movement expressed through home ranges or space-use can offer insights into spatial and habitat requirements. However, different classes of estimation methods are currently instinctively applied to answer home range, space-use or movement-based research questions regardless of their widely varying outputs, directly impacting conclusions. Recent technological advances in animal tracking (GPS and satellite tags), have enabled new methods to quantify animal space-use and movement pathways, but so far have primarily targeted mammal and avian species.MethodsMost reptile spatial ecology studies only make use of two older home range estimation methods: Minimum Convex Polygons (MCP) and Kernel Density Estimators (KDE), particularly with the Least Squares Cross Validation (LSCV) and reference (href) bandwidth selection algorithms. These methods are frequently applied to answer space-use and movement-based questions. Reptile movement patterns are unique (e.g., low movement frequency, long stop-over periods), prompting investigation into whether newer movement-based methods –such as dynamic Brownian Bridge Movement Models (dBBMMs)– apply to Very High Frequency (VHF) radio-telemetry tracking data. We simulated movement data for three archetypical reptile species: a highly mobile active hunter, an ambush predator with long-distance moves and long-term sheltering periods, and an ambush predator with short-distance moves and short-term sheltering periods. We compared traditionally used estimators, MCP and KDE, with dBBMMs, across eight feasible VHF field sampling regimes for reptiles, varying from one data point every four daylight hours, to once per month.ResultsAlthough originally designed for GPS tracking studies, dBBMMs outperformed MCPs and KDE href across all tracking regimes in accurately revealing movement pathways, with only KDE LSCV performing comparably at some higher frequency sampling regimes. However, the LSCV algorithm failed to converge with these high-frequency regimes due to high site fidelity, and was unstable across sampling regimes, making its use problematic for species exhibiting long-term sheltering behaviours. We found that dBBMMs minimized the effect of individual variation, maintained low error rates balanced between omission (false negative) and commission (false positive), and performed comparatively well even under low frequency sampling regimes (e.g., once a month).ConclusionsWe recommend dBBMMs as a valuable alternative to MCP and KDE methods for reptile VHF telemetry data, for research questions associated with space-use and movement behaviours within the study period: they work under contemporary tracking protocols and provide more stable estimates. We demonstrate for the first time that dBBMMs can be applied confidently to low-resolution tracking data, while improving comparisons across regimes, individuals, and species.

The challenges facing resident hunting in western Tanzania: the case of the Ugalla ecosystem

The legal subsistence hunting scheme (resident hunting) in Tanzania was temporarily banned in 2015 because it was considered ineffective. So far, no attempt has been made to understand the challenges facing the scheme, especially from the hunters’ perspective. This study used 8 hunter focus groups (in total, 73 hunters) and 26 key informants in the Ugalla ecosystem of western Tanzania–from June to September, 2017–to determine the challenges faced by the resident hunting scheme before the ban, and the areas of the scheme that participants felt required improvement. Focus group discussions and key informant interviews were digitally recorded. In general, study participants perceived that resident hunting regulations were poorly enforced, leading to a number of incidents such as the killing of unauthorized game, hunting outside specified areas, false reporting of animals killed, and overshooting of quotas. They noted that hunting areas were under pressure from poaching, and encroachment by pastoralists and subsistence farmers. Conflicts over hunting areas and hunting rights between resident and trophy hunters were common. Participants recommended capacity strengthening to effectively administer resident hunting, through ensuring availability of human and financial resources. They perceived active hunter engagement as the best way to deal with poaching and non-compliant behaviour by hunters. Measures to guarantee coexistence between resident and trophy hunters were recommended, for example, a thorough review of hunting area boundaries to minimize hunting area conflicts. Further study should consider the impact of hunting on wildlife in hunting areas in relation to the issues reported in this study.

Venturing out safely: The biogeography of Homo erectus dispersal out of Africa

The dispersal of Homo erectus out of Africa at some 1.9 million years ago is one of the most important, crucial, and yet controversial events in human evolution. Current opinions about this episode expose the contrast between those who see H. erectus as a highly social, cooperative species seeking out new ecological opportunities to exploit, and those preferring a passive, climate driven explanation for such an event. By using geostatistics techniques and probabilistic models, we characterised the ecological context of H. erectus dispersal, from its East African origin to the colonization of Eurasia, taking into account both the presence of other large mammals and the physical characteristics of the landscape as potential factors. Our model indicated that H. erectus followed almost passively the large herbivore fauna during its dispersal. In Africa, the dispersal was statistically associated with the presence of large freshwater bodies (Rift Valley Lakes). In Eurasia, the presence of H. erectus was associated with the occurrence of geological outcrops likely yielding unconsolidated flint. During the early phase of dispersal, our model indicated that H. erectus actively avoided areas densely populated by large carnivores. This pattern weakened as H. erectus dispersed over Europe, possibly because of the decreasing presence of carnivores there plus the later acquisition of Acheulean technology. During this later phase, H. erectus was associated with limestone and shaley marl, and seems to have been selecting for high-elevation sites. While our results do not directly contradict the idea that H. erectus may have been an active hunter, they clearly point to the fact that predator avoidance may have conditioned its long-distance diffusion as it moved outside Africa. The modelled dispersal route suggests that H. erectus remained preferentially associated with low/middle latitude (i.e., comparatively warm) sites throughout its colonization history.

Country food sharing networks, household structure, and implications for understanding food insecurity in Arctic Canada

ABSTRACTWe examine the cultural context of food insecurity among Inuit in Ulukhaktok, Northwest Territories, Canada. An analysis of the social network of country food exchanges among 122 households in the settlement reveals that a household’s betweenness centrality—a measure of brokerage—in the country food network is predicted by the age of the household. The households of married couples were better positioned within the sharing network than were the households of single females or single males. Households with an active hunter or elder were also better positioned in the network. The households of single men and women appear to experience limited access to country food, a considerable problem given the increasing number of single-adult households over time. We conclude that the differences between how single women and single men experience constrained access to country foods may partially account for previous findings that single women in arctic settlements appear to be at particular risk for food insecurity.

Were large carnivorans and great climatic shifts limiting factors for hominin dispersals? Evidence of the activity of Pachycrocuta brevirostris during the Mid-Pleistocene Revolution in the Vallparadís Section (Vallès-Penedès Basin, Iberian Peninsula)

Abstract The chronology of the first human dispersal out of Africa and the ecological role of the genus Homo in Europe as a scavenger or an active hunter during the late Early Pleistocene are two of the paleoanthropological topics most hotly debated during the last decades. The earliest human occurrences in Western Europe are recorded in the Iberian Peninsula by the late Villafranchian (1.4–1.2 Ma), during a period of climatic stability. However, currently available taphonomic and paleoecological data suggest a direct and intense competition for food resources between these human populations and the large scavenging hyaenid Pachycrocuta brevirostris. The Villafranchian was followed by the Epivillafranchian (ca. 1.2–0.8 Ma), a period of climatic instability dominated by several strong glacial periods. The evidence from the Vallparadis Section reported here suggests that such unstable climatic conditions did not affect to a great extent the composition of the large mammal assemblages and, particularly, that of the carnivore guild. Based on the impressive record of carnivoran remains recovered from the Vallparadis Section and the taphonomic interpretation of this assemblage, we suggest that the putative direct competition between early Homo and large carnivores, especially P. brevirostris, persisted throughout the late Villafranchian and the Epivillafranchian.

Body size and seasonal body condition in two small coexisting desert snake species, the Saharan sand viper (Cerastes vipera) and the crowned leafnose (Lytorhynchus diadema)

The Saharan sand viper, Cerastes vipera, and the crowned leafnose, Lytorhynchus diadema, are small coexisting psammophilic desert snake species, consume primarily lizards and do not engage in male to male combat. They differ in that C. vipera is ovoviparous and L. diadema is oviparous, C. vipera moves by sidewinding while L. diadema uses serpentine movement and C. vipera is a sit-and-wait ambusher while L. diadema is an active hunter. Results showed that C. vipera was heavier than L. diadema per unit snout-vent length (SVL). We concluded that this was related to foraging, as L. diadema had to move quicker than L. diadema, and to reproduction, as C. vipera needed more abdominal space for developing embryos. Sexual size dimorphism was found in adults in both species and it appeared that ecological advantages took precedence over phylogenetic affinity in determining size differences. The relatively small size, ovoviparity, sandy habitat with sidewinding, and lack of male to male combat for C. vipera whereas oviparity and sandy habitat for L. diadema may explain partly sexual size dimorphism in these species. Females showed seasonal fluctuations in BCI in both species but males did not and C. vipera females showed greater fluctuations than L. diadema females. We concluded that the former resulted from higher energy costs of females than males and the latter because ovoviparity is costlier than oviparity.

Temporal activity and dietary selection in two coexisting desert snakes, the Saharan sand viper (Cerastes vipera) and the crowned leafnose (Lytorhynchus diadema)

The Saharan sand viper (Cerastes vipera) and the crowned leafnose (Lytorhynchus diadema) are two snake species well adapted to desert sand dunes and, in Israel, coexist in the western Negev Desert. C. vipera is a sit-and-wait ambusher while L. diadema is an active hunter. We studied the seasonal and diel activity patterns and dietary selection of these two species while free-living in the field. Both species were active from early spring until late fall but displayed (i) different seasonal activity patterns –C. vipera was bimodal with peaks in spring and autumn whereas L. diadema was basically unimodal with a peak in summer; (ii) different nocturnal above-ground activity patterns –C. vipera was active mainly during the first three hours of darkness while L. diadema was constantly active during the first seven hours of darkness; and (iii) different patterns of nocturnal behavior –C. vipera moved up to 50m while L. diadema moved several hundred meters each night. Dietary selection differed between these snake species although lizards, mainly Nidua fringe-fingered lizards (Acanthodactylus scutellatus), were the main dietary item for both. We concluded that temporal partitioning in above-ground activity, different foraging strategies and differences in dietary selection may contribute towards the coexistence of the two snake species.

The Prevalence of Food Insecurity Is High and the Diet Quality Poor in Inuit Communities 3

Indigenous peoples experience a disproportionate burden of food insecurity and the Arctic is no exception. We therefore evaluated the prevalence, socio-demographic, and dietary correlates of food insecurity in the most comprehensive assessment of food insecurity in Arctic Canada. A cross-sectional survey of 1901 Inuit households was conducted in 2007–2008. Measurements included food insecurity, 24-h dietary recalls, socio-demographics, and anthropometry. Food insecurity was identified in 62.6% of households (95% CI = 60.3–64.9%) with 27.2% (95% CI = 25.1–29.3%) of households severely food insecure. The percent with an elevated BMI, waist circumference, and percent body fat was lower among individuals from food insecure households compared to food secure households (P≤ 0.001). Adults from food insecure households had a significantly lower Healthy Eating Index score and consumed fewer vegetables and fruit, grains, and dairy products, and consumed a greater percent of energy from high-sugar foods than adults from food secure households (P≤ 0.05). Food insecurity was associated with household crowding, income support, public housing, single adult households, and having a home in need of major repairs (P≤ 0.05). The prevalence of having an active hunter in the home was lower in food insecure compared to food secure households (P≤ 0.05). Food insecurity prevalence is high in Inuit communities, with implications for diet quality that over the long-term would be anticipated to exacerbate the risk of diet-related chronic diseases. Actions are required to improve food security that incorporate the traditional food system and healthy market food choices.

Osteological evidence for predatory behavior of the giant percrocutid (Dinocrocuta gigantea) as an active hunter

We present osteological evidence that a rhinocerotid skull belonging to a female Chilotherium wimani was bitten by a giant percrocutid, Dinocrocuta gigantea. Aided by comparative evidence of black rhino (Diceros bicornis) predation by extant spotted hyenas Crocuta crocuta, we interpret the healed wound on the C. wimani female as an injury incurred by the late Miocene D. gigantea. The hunting paleoecology of the giant percrocutid D. gigantea has long been speculated, but thus far no clear evidence has been discovered to point to the predatory habits of this carnivore. The present specimen of C. wimani provides evidence to indicate that the giant percrocutid shared similarities in predatory behavior to the modern spotted hyena: it was an active hunter in spite of the specialized bone-cracking craniodental morphology which imparted superb capability for processing bone.

Digital holographic microscopy reveals prey-induced changes in swimming behavior of predatory dinoflagellates

The shallow depth of field of conventional microscopy hampers analyses of 3D swimming behavior of fast dinoflagellates, whose motility influences macroassemblages of these cells into often-observed dense "blooms." The present analysis of cinematic digital holographic microscopy data enables simultaneous tracking and characterization of swimming of thousands of cells within dense suspensions. We focus on Karlodinium veneficum and Pfiesteria piscicida, mixotrophic and heterotrophic dinoflagellates, respectively, and their preys. Nearest-neighbor distance analysis shows that predator and prey cells are randomly distributed relative to themselves, but, in mixed culture, each predator clusters around its respective prey. Both dinoflagellate species exhibit complex highly variable swimming behavior as characterized by radius and pitch of helical swimming trajectories and by translational and angular velocity. K. veneficum moves in both left- and right-hand helices, whereas P. piscicida swims only in right-hand helices. When presented with its prey (Storeatula major), the slower K. veneficum reduces its velocity, radius, and pitch but increases its angular velocity, changes that reduce its hydrodynamic signature while still scanning its environment as "a spinning antenna." Conversely, the faster P. piscicida increases its speed, radius, and angular velocity but slightly reduces its pitch when exposed to prey (Rhodomonas sp.), suggesting the preferred predation tactics of an "active hunter."

Including Spatial Heterogeneity and Animal Dispersal When Evaluating Hunting: a Model Analysis and an Empirical Assessment in an Amazonian Community

: Hunting in tropical forests is typically most intense near human settlements, and this creates gradients of decreasing animal densities toward those settlements. Within the context of this spatial pattern, we evaluated the status of game in the hunting grounds of an indigenous community in eastern Ecuador. We constructed a spatially explicit model of hunter‐prey interactions that mimicked the hunting in the village and included realistic animal‐dispersal rules. We compared predictions from the model with distributions of animal harvest rates and catch per unit effort of 12 game species. Six species were overharvested in part or all of the area, and two other species were probably being overharvested, although high dispersal rates complicated the interpretation. We then compared our method with methods that have been used previously. We argue that because our method provides information about the spatial extent of overharvesting, it could be particularly useful in informing decision makers about where to establish no‐take areas and could therefore aid in improving the sustainability of hunting in tropical forests.

Illuminatinganoverlooked hunting stakeholder group: Nonhunters and their interest in hunting

Abstract While the traditional sport hunter wildlife management constituency appears to be declining, little is known about another group of hunting stakeholders—nonhunters who know hunters, participate in hunting‐related activities, have positive beliefs about hunting, and perceive benefits from hunting. This study explored New York State nonhunters’ experiences with and perceptions of hunting, using interview and mailed questionnaire data collection techniques. Many nonhunters know hunters and participate in hunting‐related activities. Roughly one‐third of nonhunters had positive beliefs about the utility of hunting as a wildlife management tool, and over 10% received benefits from hunting. These variables were significantly related to participation in hunting‐related activities with hunters. The size of the core nonhunter stakeholder population is estimated to be roughly equal to the active hunter population. These results suggest implications for wildlife managers as well as potential problems with traditional recreation‐based research treatments of hunting.