Kernel Utilization Distributions Research Articles

Aspects of Movement Ecology and Habitat Use of Migratory Raptors Using Satellite Telemetry from India to Central Asia

Single individuals of the Greater Spotted Eagle (Clanga clanga), Indian Spotted Eagle (Clanga hastata), Tawny Eagle (Aquila rapax), Western Marsh Harrier (Circus aeruginosus), and two Pallid Harriers (Circus macrourus) were deployed with satellite transmitters in 2021 to study their home ranges, habitat associations, movement, and migration patterns. Data were collected for a combined number of 2291 days, providing 84,544 locations. Home ranges were calculated as kernel utilization distributions and expressed as 95% KDE and core areas as 50% KDE. Overall, eagles had larger home ranges (mean ± SD) of 942.70 ± 937.83 km2 compared to harriers, 43.84 ± 35.55 km2. Among eagles, the Greater Spotted Eagle had the largest home-range size of 2147.03 km2 calculated in Kazakhstan, while the female Pallid Harrier had the smallest home range of 5.74 km2 in Russia. Daily and monthly distances varied among eagles and harriers. The female Pallid Harrier covered the longest average monthly distance of 8585.43 ± 11,943.39 km, while the shortest monthly distance of 1338.22 ± 716.38 km was traveled by the Indian Spotted Eagle. All tagged birds migrated toward higher latitudes in the Northern hemisphere, except the Indian Spotted Eagle, which migrated to Pakistan. The male Western Marsh Harrier covered the longest migration distance in a shorter span of time, while the female Pallid Harrier took the longest to cover its migration distance. Overall, the daily distance covered during migration varied from 115.09 km traveled by the Indian Spotted Eagle to an overwhelming distance of 2035.85 km covered by the male Western Marsh Harrier. Scrubs, water bodies, croplands, and settlements were important habitat features associated with eagles, while croplands, open scrub, and built-up areas were associated with the female Pallid Harrier. The male Western Marsh Harrier was found to be primarily associated with saltpans and salt-affected areas having emergent vegetation. This study presents new insights into the movement and spatial ecology of long-distance migrant raptors that winter in Western India. We provide preliminary support for the use of the Western Circum–Himalayan Corridor as one of the important corridors of the Central Asian Flyway that warrants much appreciation among the current set of flyway corridors.

Incorporating vertical movement of fishes in habitat use models.

Fish telemetry studies now routinely collect positional and depth data, yet analytical approaches that integrate three-dimensional data are limited. Here we apply the potential path volume (PPV) model, a method previously developed to estimate habitat volume based on rates of avian movement, to free-swimming fish. Using a telemetry dataset of white sucker (Catastomus commersonii) from Turkey Lake (Ontario, Canada), we evaluated the effects of the number of spatial positions and different methods of selecting swim speed (vswim), a key parameter for PPV models, on habitat volume estimates. We subsequently compared habitat volume estimates and habitat overlap among white sucker pairs from the PPV models to those calculated using kernel utilization distribution-based approaches. The number of spatial positions in the PPV model had a significant effect on habitat volume estimates, whereas the magnitude of the vswim parameter or its specificity (constant value vs. fish-season specific parameter values) did not affect habitat volume estimates. The PPV method resulted in larger habitat volume estimates and greater habitat overlap estimates among fish pairs relative to those obtained from a three-dimensional kernel utilization distribution method. The PPV model is a useful analytical tool that, by incorporating potential animal movement into habitat use evaluations, can help answer key ecological questions and provide insight into fish space use in a wide range of conservation and management applications.

Ontogenetic changes in green turtle (Chelonia mydas) diet and home range in a tropical lagoon

Ontogenetic changes in habitat and diet are widespread among marine species. Most species of sea turtles are characterized by extreme ontogenetic changes in habitat use and diet, with large changes occurring in early developmental stages (e.g., neonates to juveniles). Changes can continue even after recruitment to shallow coastal habitats. In places where substantial transitions in habitat occur across short distances, it is possible that the distances of developmental movements from one habitat to another could be short. We investigated ontogenetic changes in home range size, home range location and diet of Chelonia mydas in a tropical coastal lagoon in north-western Australia by combining acoustic telemetry with stable isotope analysis. There was a substantial (but nonlinear) increase in home-range size (kernel utilization distribution: KUD) with length, and an increase in the average distance of the center of home ranges from shore with length: larger turtles tended to occupy larger areas further from the shore. These patterns were accompanied by complex nonlinear changes in δ13C, δ15N and δ34S of red blood cells and nails; changes were rapid from 36 cm (the length of the smallest individual captured) to 50 cm, before reversing more gradually with increasing size. δ15N and δ34S (but not δ13C) of red blood cells and nails increased monotonically with KUD and distance from shore. Seagrass was likely an important food for all sizes, macroalgae was potentially important for small (< 60 cm CCL) individuals, and the proportion of scyphozoan jellyfish in diet increased monotonically with size. The combination of acoustic telemetry and stable isotope analysis revealed ontogenetic shifts in use of space and diet across short distances in a tropical coastal lagoon.

Omega-3 enriched chick diet reduces the foraging areas of breeders in two closely related shearwaters from contrasting marine environments.

Seabirds have evolved several life-history characteristics to help buffer environmental stochasticity. However, particularly during the breeding season, seabirds may be affected by reductions in prey availability and localised oceanographic conditions caused by variations in the environment. The increase in sea surface temperature, triggered by accelerated global warming, is impairing phytoplankton production of omega-3 fatty acids (FAs). Here, we assessed the ecological role of omega-3 FAs on chick development and subsequently on breeder foraging behaviour in two closely related shearwater species foraging in contrasting marine environments. We supplemented chicks with omega-3 FA pills or with control placebo pills and monitored chick growth, chick health status and breeder at-sea foraging behaviour using global positioning system devices. We found that omega-3 chick supplementation reduced the 95% kernel utilization distribution of short trips of Cape Verde shearwaters, but overall, breeders kept a similar foraging pattern between treatments, potentially influenced by predictable prey patches off the West African coast. In contrast, for Cory's shearwaters, the parents of the omega-3 group greatly reduced the foraging effort. This suggests that the proximity to productive prey patches around the colony may help birds to adjust their effort and, therefore, energy expenditure, to changes in the development of their offspring, as driven by their nutritional status. Overall, our results suggest a link between a chick diet enriched in omega-3 FAs and parental foraging effort, providing insight into their ability to cope with a changing and increasingly stochastic marine environment.

Acoustic telemetry system as a novel approach for evaluating the effective attraction of fish to artificial reefs

Due to there being a lack of suitable approaches for evaluating the effectiveness of artificial reefs, two experiments were designed to examine the feasibility of acoustic telemetry, a rapidly developing method for tracking aquatic animals. The first experiment was conducted to understand the deployment procedures of an acoustic telemetry system and determine the appropriate deployment of receivers’ spacing, while the second experiment was conducted to quantify the site fidelity and habitat use of 11 reef fish in the Fangchenggang artificial reef area in the northern South China Sea, China. The results indicated that the logistic regression model was an effective way to balance the detection probability at different distances between the range test transmitter and receiver, with above 50% detection probability within 240 m and 80% detection probability within 110 m. The residency index, as a quantification of site fidelity, was 0.85 ± 0.24. The 100% minimum convex polygon, 95% kernel utilization distribution, and 50% kernel utilization distribution, which are the indicators of habitat use, were 34,522.94 ± 35,548.95, 1,467.52 ± 1,619.05, and 236.01 ± 294.59 m2, respectively. High site fidelity and the small spatial scale of habitat use for reef fish demonstrated that artificial reefs were an effective man-made structure to attract fish. Overall, this study supports the feasibility of the acoustic telemetry system, indicating that it provides a good approach for quantifying the associations between artificial reefs and fish.

Influence of Hurricane Activity on Acoustic Array Efficiency: A Case Study of Red Snapper within an Artificial Reef Complex

AbstractMeteorological disturbances, such as hurricanes, can cause wide distributional changes to fish populations, but studies documenting fish movement in response to these disturbances are rare and serendipitous. We opportunistically examined how a hurricane influenced behavior of Red Snapper Lutjanus campechanus at an artificial reef complex in the western Gulf of Mexico. Red Snapper had a variety of responses, with some fish emigrating and some remaining on site during Hurricane Harvey—a category 4 storm. Hurricane‐induced destruction or alteration of habitat may alter space use behavior of fish. However, caution should be used when interpreting behavior without the inclusion of array performance, which may change due to environmental conditions. Importantly, when acoustic array efficiency was not accounted for in space use analyses, mean kernel utilization distribution (m3) was marginally different among the periods before, during, and after Hurricane Harvey. However, when mean daily array efficiency was included as a covariate, space use among the three periods was not significantly different. Hurricanes can affect the movement and residency of marine species and can be an important driver in the displacement of populations and degradation of habitats, but array efficiency should be incorporated to prevent misinterpreting the behaviors of tagged fish.

ANALYSIS OF LONG-TAILED MONKEY ROAMING AREA (Macaca fascicularis) IN MENIPO NATURAL TOURISM PARK, ENORAEN VILLAGE, EAST AMARASI SUBDISTRICT, KUPANG REGENCY, EAST NUSA TENGGARA PROVINCE

monkeys (Macaca fascicularis). This research was conducted at Menipo Natural Tourism Park (NTP), Enoraen Village, East Amarasi Subdistrict, Kupang Regency, East Nusa Tenggara which was conducted for 1 month, from September to October 2021. The study used Zoatrack's WebGIS method, which determined Macaca’s home range using Minimum Concex Polygon (MCP) method and core area using Kernel Utilization Distribution. Moreover, the analysis of data were conducted with statistics descriptive analysis. The results showed that the home range that has been analyzed using Minimum Convex Polygon (MCP) is 142.45 ha and this area of long-tailed monkeys (Macaca fascicularis) home range lies in almost all of the Menipo NTP area with its forest characteristics that consists of dry forests, brackish forests, and coastal forests. The results of the core area analysis using Kernel Utilization Distribution showed that the area of the core area was 53.63 Ha. The results of the core area also shows that there is one particular of core area that is often visited by long-tailed monkeys (Macaca fascicularis). This is due to the abundance of food and trees as their resting place in the Menipo NTP area.

Satellite Telemetry Elucidates Migratory Pathways and Foraging Areas for Hawksbill Sea Turtles, Eretmochelys imbricata, in the Caribbean

Adult female sea turtles are highly migratory, moving between foraging and nesting areas that can be thousands of kilometers apart. Conserving sea turtles and their habitats therefore depends on knowledge of space use across these migration-linked environments. Here, we describe migratory behavior of hawksbill sea turtles (Eretmochelys imbricata), a globally imperiled species. We used satellite telemetry to characterize the movements of females from nesting areas in Jamaica (n = 4) and Antigua (n = 4), West Indies, over 1998–2001. We mapped migrations and summarized space use during inter-nesting and foraging periods with kernel utilization distributions (UDs) and minimum convex polygons. Seven of eight turtles made post-nesting migrations, with paths ranging 56–1324 km in length, representing straight-line displacements of 68–1206 km. Two turtles sampled in southern Jamaica made short-range migrations within southern Jamaican waters, whereas two from northern Jamaica migrated further to foraging areas in the waters of Belize and Honduras. Three migrants sampled at Long Island, Antigua migrated to St. Eustatius, St. Kitts, and Redonda, respectively, with a fourth individual remaining resident in northeastern Antigua. Inter-nesting movements observed for three turtles produced 50% UDs ranging 12–44 km2, with centroid depths between 4–13 m. Foraging UDs for seven turtles spanned 8–111 km2 and 2–161 m in depth. Our results reveal variable migratory strategies, demonstrate international connectivity between hawksbill foraging and nesting habitats, and provide important information for Caribbean conservation efforts such as the design of protected areas or fisheries policies.

Fine‐scale movement and habitat use of juvenile, subadult, and adult green turtles (Chelonia mydas) in a foraging ground at Ningaloo Reef, Australia

Abstract The residence, home range, and habitat use of juvenile (42.0–63.5 cm midline curved carapace length, CCL), subadult (68.6–84.6 cm CCL), and adult (81.9–104.2 cm CCL) green turtles (Chelonia mydas) was investigated using passive acoustic telemetry in Ningaloo Marine Park, north‐western Australia. Eighty‐one turtles ranging in size from 42 to 104 cm CCL were captured on their foraging grounds and tagged with acoustic tags. Individuals were monitored for up to 913 days (range 48–913 days, median 367 days). Turtles of all sizes demonstrated very high fidelity to their foraging area. Residence declined with turtle body size and home range increased with turtle body size, with an average 50% kernel utilization distribution (KUD) area of 0.29, 0.47, and 0.57 km2 for juveniles, subadults, and adults, respectively. Juveniles occurred only in shallow inshore habitat dominated by seagrass and macroalgae‐covered pavement. Subadults and adults selected macroalgae‐covered pavement, sandy areas of the lagoon, and macroalgae‐dominated patch reefs within the lagoon. At high tide, juveniles were approximately 200 m closer to the shore than at low tide, but there was no tidal pattern of space use in subadult and adult turtles. Less than 5% of turtles departed the array within 6 months and there was no evidence of developmental migrations in subadults. The results highlight the conservation potential for go‐slow areas to minimize boat strike in areas of high turtle density, given the small and stable home ranges. Furthermore, the spatial segregation of juveniles, subadults, and adults will result in variability in the susceptibility of individuals to boat strike. The influencing factors that drive the developmental migrations of turtles to consecutive habitats as they grow, as well as movement away from foraging grounds in response to changes in habitat quality, are complex. The ability of acoustic telemetry to provide long‐term data on all size classes of turtles within foraging areas provides a tool to enable the long‐term monitoring of turtle populations, which is required for at‐risk populations and/or habitats.

Female and male Eurasian lynx have distinct spatial tactics at different life-history stages in a high-density population.

Knowledge regarding the spatial behavior of the Eurasian lynx is mainly inferred from populations in Europe. We used GPS telemetry to record the spatial behavior of nine individuals in northwestern Anatolia obtaining eleven home ranges (HRs). Analyses revealed the smallest mean HR sizes (nHR ♀ = 4) at 57 km2 (95% kernel utilization distribution, KUD) and 56 km2 (95% minimum convex polygon, MCP), ever reported for adult female Eurasian lynx. Adult males either occupied small permanent territories (nHR♂.T = 2), with a mean of 176 km2 (95% KUD) and 150 km2 (95% MCP), or were residents without territories (floaters, nHR♂. F = 2) roaming across large, stable HRs with a mean size of 2,419 km2 (95% KUD) and 1,888 km2 (95% MCP), comparable to HR sizes of Scandinavian lynx populations. Three disperser subadult males did not hold stable HRs (mean 95% KUD = 203 km2, mean 95% MCP = 272 km2). At 4.9 individuals per 100 km2, population density was one of the highest recorded, suggesting that the presence of adult male floaters was a consequence of a landscape fully occupied by territorials and revealing a flexibility of spatial behavior of Eurasian lynx not previously recognized. Such a high population density, small HRs, and behavioral flexibility may have been aided by the legal protection from and apparent low levels of poaching of this population. The observed spatial tactics are unlikely to be seen in most of the previously studied Eurasian lynx populations, as they either suffer medium to high levels of human‐caused mortality or were unlikely to be at carrying capacity. For effective and appropriate conservation planning, data from felid populations in a reasonably natural state such as ours, where space, density, prey, and pathogens are likely to be the key drivers of spatial dynamics, are therefore essential.

Spatial ecology of hawksbill sea turtles (Eretmochelys imbricata) in foraging habitats of the Gulf of California, Mexico

Understanding movement patterns and habitat preferences of endangered species during their most vulnerable life stages is a key step to developing effective conservation strategies that prevent extinctions. Hawksbills (Eretmochelys imbricata) are among the most-imperiled sea turtles and are generally thought to associate with very specific coral and rocky reef habitats. However, in the Eastern Pacific, hawksbills have also been found to have a strong association with mangrove estuaries. Eastern Pacific hawksbills constitute one of the most endangered sea turtle populations globally, and the Gulf of California, Mexico, was recently identified as a potentially important foraging region. Here we analyzed movement patterns of 12 individuals equipped with Argos-linked GPS transmitters. We calculated home ranges using kernel density estimations and found that hawksbills were highly restricted in their movements, spending months to years in areas ranging from 0.05 to 17 km2. Mean sizes of 50% and 95% kernel utilization distributions were 0.72 km2 and 3.8 km2, respectively. Also, 85.6% of hawksbill locations were associated within, or in close proximity to, mangrove estuaries, further highlighting the importance of these fragile ecosystems for hawksbill conservation. The fine-scale resident behavior of hawksbill turtles in foraging grounds presents a unique conservation opportunity while also underscoring the need to identify these sites and work with local communities to protect them.

Fishers as foragers: Individual variation among small-scale fishing vessels as revealed by novel tracking technology

Effective fisheries management requires an understanding of fisher behavior. Though vessel tracking systems are increasingly used to describe the movements and activities of industrial fishing fleets, their use has been limited within the small-scale fisheries employing the vast majority of the world’s capture fishers. Here we combine novel vessel tracking technology with logbook data to conduct a high-resolution analysis of behavior and decision-making within a small-scale fishery. Our results indicate significant heterogeneity in fisher behavior, catch composition, and profits within a small-scale fleet operating in the central Gulf of California, even amongst fishing vessels using similar gear types. The weekly home ranges (75 % Kernel Utilization Distribution) occupied by fishers spanned 1.5–1121.8 km2 across 13 vessels, while weekly profits ranged from -1810 to 26,160 pesos. Differences in the spatial interactions and catch profiles of observed vessels revealed the existence of behavioral associations linked with distinct fishing strategies. After identifying and describing the contextual factors driving such heterogeneity among vessels using hook and line fishing gear, we interpret emergent patterns and processes using insights from foraging theory and marine social science. In illustrating the applications and opportunities presented by recent advances in vessel tracking technology, we argue for the use of spatially explicit analytical approaches in assessing behavioral diversity within small-scale fisheries and in designing robust and equitable management strategies.

Hunting territories and land use overlap in sedentarised Baka Pygmy communities in southeastern Cameroon

A significant number of Baka Pygmies in Cameroon have been sedentarised in roadside villages, in contrast to their nomadic hunter-gatherer existence of the past. Although this change in lifestyle has had important consequences on health, most Baka villages still supplement their diets from forest products, especially wild meat. We used a combination of participatory methods and monitoring of individual hunters to map hunting territories in 10 Baka villages in southeastern Cameroon. From these, we determined whether wild meat extraction levels per village were related to the size of hunting territories, measured habitat use by hunters and finally defined the overlap between hunting territories and extractive industries in the region. Mapped village hunting areas averaged 205.2 ± 108.7 km2 (range 76.8–352.0 km2); all villages used a total of 2052 km2. From 295 tracks of 51 hunters, we showed that hunters travelled an average of 16.5 ± 13.5 km (range 0.9–89.8 km) from each village. Home ranges, derived from kernel utilization distributions, were correlated with village offtake levels, but hunter offtake and distance travelled were not significantly related, suggesting that enough prey was available even close to the villages. Hunters in all village areas exhibited a clear bias towards certain habitats, as indicated by positive Ivlev’s index of selectivity values. We also showed that all village hunting territories and hunter home ranges fall within mining and logging concessions. Our results are important for local understanding of forest land uses and to reconcile these with the other land uses in the region to better inform decisions concerning land use policy and planning.

Movement and habitat use of striped marlin Kajikia audax in the Western Indian Ocean.

Striped marlin Kajikia audax are globally Near Threatened and their stock in the Indian Ocean was last assessed as "overfished and subject to overfishing". Significant gaps in our understanding of their ecology remain, hampering the efforts of fisheries managers to ensure stock sustainability. There is a particular lack of fisheries-independent data. Here we present the results from the first large-scale satellite tracking study of K. audax in the Indian Ocean. We tagged 49 K. audax with pop-up archival satellite-linked tags off the Kenyan coast from 2015 to 2019. Individuals were highly mobile, covering horizontal distances of up to 9187 km over periods ranging up to 183 days, with a mean daily distance of ~48 km. Long-distance movements were recorded to the east and north of East Africa, with the most distant tracks extending north to the Arabian Sea and east to near the Maldives. None of the K. audax swam south of East Africa. Kernel utilization distributions of fish locations demonstrated their shifting seasonal activity hotspots. Over the sport-fishing season (and tagging period) in Kenya, from December to March, K. audax typically stayed off the East African coast. After March, the activity hotspot shifted north to a region close to the Horn of Africa and Socotra Island. Remotely sensed sea surface temperature and chlorophyll-a maps indicated that this seasonal movement could be driven by a shift in prey availability. Our results show the high mobility of K. audax in the Western Indian Ocean, and that individuals seasonally range between two major fishing areas.

Movement, home range, and depredation of invasive lionfish revealed by fine-scale acoustic telemetry in the northern Gulf of Mexico

Fine-scale movement dynamics of adult invasive lionfish may inform the spatial scale of negative impacts to local food webs, the design and efficacy of ongoing removal efforts, and the speed at which lionfish may spread into new habitats, but have not previously been characterized. An acoustic Vemco positioning system (VPS) was used to track fine-scale (<10 m) movements of adult lionfish (288–395 mm total length; n = 20) tagged in situ at artificial reefs off Destin, Florida (USA). We estimated the spatial scale of movement, activity patterns, and individual home ranges, as well as whether these variables were affected by lionfish size or density. Lionfish were tracked up to 89 days and had 95% kernel utilization distribution (KUD) home ranges between 158 and 4051 m2. Daily distances moved (range 93–807 m) exceeded previous estimates, and 40% of tagged lionfish were tracked moving to reefs up to 2 km from initial tagging locations. Movement pattern and velocity data revealed two (10%) tagged lionfish were consumed by fast-moving predators, while another two emigrated outside the array. Acoustic detection of the remaining tagged fish ended prematurely following two hurricanes that passed over the array, which may implicate the storms in displacing tagged fish, causing tag loss, or contributing to lionfish mortality. Overall, results suggest invasive lionfish have larger home ranges and display greater movement than reported previously which has important implications for artificial reef management in Florida, and elsewhere, in response to the lionfish invasion.

No Place Like Home? High Residency and Predictable Seasonal Movement of Whale Sharks Off Tanzania

Highly mobile marine megafauna species, while widely distributed and frequently threatened, often aggregate in distinct localized habitats. Implementation of local management initiatives within these hotspots is more achievable than developing effective conservation strategies that encompass their entire distributions. Such measures have the potential for disproportionate population-level benefits but rely on a detailed understanding of spatiotemporal habitat use. To that end, we examined the residency and small-scale habitat use of 51 whale sharks (Rhincodon typus) over 5 years at an aggregation site in Tanzania using passive acoustic telemetry. Whale sharks were highly resident within and across years, with a combined maximum residency index of 0.39. Although fewer sharks were detected from March to September, residency was high throughout the year. Ancillary photographic-identification data showed that individual residency persisted before and after tag attachment. Kernel utilization distributions and movement networks both revealed the same spatiotemporal pattern of habitat use, with a small core habitat (50% KUD area for all sharks combined = 12.99 km2) that predictably changed on a seasonal basis. Activity spaces did not differ with time of day, sex or size of the sharks, indicating a population-level pattern driven by prey availability. The small and predictable core habitat area at this site means that site-based management options to reduce shark injuries and mortality from boat strike and fishing gear entanglement can be spatially targeted for maximum effectiveness and compliance by human users.

Identifying Birds' Collision Risk with Wind Turbines Using a Multidimensional Utilization Distribution Method

ABSTRACTRenewable energy plays a key role in reducing greenhouse gas emissions. However, the expansion of wind farms has raised concerns about risks for bird collisions. We tested different methods used to understand whether birds' flight occurs over wind turbines and found kernel density estimators outperform other methods. Previous studies using kernel utilization distribution (KUD) have considered only the 2 horizontal dimensions (2D). However, if altitude is ignored, an unrealistic depiction of the situation may result because birds move in 3 dimensions (3D). We quantified the 3D space use of the Griffon vulture (Gyps fulvus) in El Estrecho natural park in Tarifa (southern Spain, on the northern shore of the Strait of Gibraltar) during 2012–2013, and, for the first time, their risk of collision with wind turbines in an area in the south of Spain. The 2D KUD showed a substantial overlap of the birds' flight paths with the wind turbines in the study area, whereas the 3D kernel estimate did not show such overlap. Our aim was to develop a new approach using 3D kernel estimation to understand the space use of soaring birds; these are killed by collision with wind turbines more often than any other bird types in southern Spain. We determined the probability of bird collision with an obstacle within its range. Other potential application areas include airfields, plane flight paths, and tall buildings. © 2020 The Authors. Wildlife Society Bulletin published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.

The influence of a single species on the space use of mixed-species flocks in Amazonian Peru

BackgroundThe drivers of space use patterns of multi-species groups have been poorly studied, although mixed-species avian flocks are common throughout the world. In a mixed-species flock, multiple species move together and maintain proximity. The different species may or may not have conflicting preferences of space use. We hypothesized that the space use patterns of the flock are driven by a single species.MethodsWe investigated the behavioral drivers of space use patterns of mixed-species flocks in Amazonian Peru by mapping 95% fixed-kernel home ranges of three flocks, which then we divided into high-use (inner 55% kernel utilization distribution) and low-use areas (lying outside the high-use area). We quantified the foraging and anti-predator behavior of individual birds in the flocks. We tested whether foraging and anti-predator behavior of different species were different in high use and low use areas of the flock.ResultsWe collected 455 spatial points and 329 foraging and anti-predator behavior observations on three flocks. The single best model for explaining the space use patterns of the flocks contained only vegetation density that surrounded Dusky-throated Antshrikes.ConclusionThe results are consistent with the hypothesis that a single species in mixed-species flocks has a disproportionately large influence on space use patterns. The surrounding vegetation density of the Dusky-throated Antshrike was the only driver of space use patterns of flocks supported by our data. The results may apply to flocks pantropically, many of which are led by species that behave similarly to the Dusky-throated Antshrike, e.g. Asian flocks led by drongos (Dicrurus spp.).

Commensal bacterial sharing does not predict host social associations in kangaroos.

Social network analysis has been postulated as a tool to study potential pathogen transmission in wildlife but is resource-intensive to quantify. Networks based on bacterial genotypes have been proposed as a cost-effective method for estimating social or transmission network based on the assumption that individuals in close contact will share commensal bacteria. However, the use of network analysis to study wild populations requires critical evaluation of the assumptions and parameters these models are founded on. We test (a) whether networks of commensal bacterial sharing are related to hosts' social associations and hence could act as a proxy for estimating transmission networks, (b) how the parameters chosen to define host associations and delineate bacterial genotypes impact inference and (c) whether these relationships change across time. We use stochastic simulations to evaluate how uncertainty in parameter choice affects network structure. We focused on a well-studied population of eastern grey kangaroos (Macropus giganteus), from Sundown National Park, Australia. Using natural markings, each individual was identified and its associations with other kangaroos recorded through direct field observations over 2years to construct social networks. Faecal samples were collected, Escherichia coli was cultured and genotyped using BOX-PCR, and bacterial networks were constructed. Two individuals were connected in the bacterial network if they shared at least one E.coli genotype. We determined the capacity of bacterial networks to predict the observed social network structure in each year. We found little support for a relationship between social association and dyadic commensal bacterial similarity. Thresholds to determine host associations and similarity cut-off values used to define E.coli genotypes had important ramifications for inferring links between individuals. In fact, we found that inferences can show opposite patterns based on the chosen thresholds. Moreover, no similarity in overall bacterial network structure was detected between years. Although empirical disease transmission data are often unavailable in wildlife populations, both bacterial networks and social networks have limitations in representing the mode of transmission of a pathogen. Our results suggest that caution is needed when designing such studies and interpreting results.

Effect of mountain gorilla (&lt;i&gt;Gorilla beringei beringei&lt;/i&gt;) population growth to their key food plant biomass in Volcanoes National Park, Rwanda

High densities of large herbivores can have detrimental effects on plant biomass. Understanding the relationship between animal densities and plant distribution and abundance is essential for the conservation of endangered species and ecosystems. Mountain gorilla censuses conducted for different periods in the last three decades have revealed a steady increase of gorilla population in Virunga Massif whereby the recent number of gorillas has doubled compared to their number in the 1980s. It is unclear whether the continuous population growth of the herbivorous Virunga gorilla within an isolated forest ‘island’ has been affecting gorilla food plant biomass. This study investigated the effect of varying mountain gorilla densities on the biomass of the five key food plant species (Galium spp., Carduus nyassanus, Peucedanum linderi, Rubus spp., Laportea alatipes) that make up &gt;70% of the mountain gorilla diet. We used plant biomass data collected in a central part of the Virunga massif, commonly known as Karisoke sector from 2009 to 2011, and GPS records of gorilla groups ranging in the same area nine months prior biomass assessment. Gorilla densities were estimated using the Kernel Utilization Distribution (KDE) analysis (functions: ‘kernelUD’ and ‘getvolumeUD’) from the Adehabitat package in R software, which provides the probability density of gorilla occurrence at each coordinate (x, y) of the study area. Analyses using GLMs suggest that gorilla densities (a proxy of previous gorilla utilization intensity) did neither affect the total biomass of key food plant species nor the biomass of each key food plant species (p&gt;0.05). These results may indicate that current revisit rates of feeding sites by gorillas allow for complete plant regeneration, and no signs of overharvesting. Alternatively, feeding sites characterized by very high biomass may be preferred by gorillas and remain sites with the highest biomass even after being frequently used by gorillas. Findings also suggest that carrying capacity of the gorilla population in the study areas may not yet be reached if food is the driving constraint. However, monitoring of the relationship between gorilla densities and food plant biomass must continue while the Virunga population continues growing. Future studies also need to incorporate other sympatric large herbivores in the Virungas who share food plants with mountain gorillas.Keywords: habitat use, gorilla density, plants biomass