Aggression and Coexistence in Female Caribou

Female caribou (Rangifer tarandus) are highly gregarious, yet there has been little study of the behavioral mechanisms that foster coexistence. Quantifying patterns of aggression between male and female, particularly in the only cervid taxa where both sexes grow antlers, should provide insight into these mechanisms. We asked if patterns of aggression by male and female caribou followed the pattern typically noted in other polygynous cervids, in which males display higher frequencies and intensity of aggression. From June to August in 2011 and 2012, we measured the frequency and intensity of aggression across a range of group sizes through focal animal sampling of 170 caribou (64 males and 106 females) on Adak Island in the Aleutian Archipelago, Alaska. Males in same-sex and mixed-sex groups and females in mixed-sex groups had higher frequencies of aggression than females in same-sex groups. Group size did not influence frequency of aggression. Males displayed more intense aggression than females. Frequent aggression in mixed-sex groups probably reflects lower tolerance of males for animals in close proximity. Female caribou were less aggressive and more gregarious than males, as in other polygynous cervid species.La femelle caribou (Rangifer tarandus) est très grégaire et pourtant, très peu d’études ont été faites sur les mécanismes du comportement qui favorisent la coexistence. Des modèles quantificateurs d’agression entre le mâle et la femelle, particulièrement chez le seul cervidé où les deux sexes possèdent des bois, devraient permettre d’en savoir plus sur ces mécanismes. Nous nous sommes demandé si les modèles d’agression entre la femelle et le mâle caribou ressemblaient aux modèles d’agression généralement remarqués chez d’autres cervidés polygynes, pour lesquels les mâles affichent une fréquence et une intensité d’agression plus grandes. De juin à août 2011 et 2012, nous avons mesuré la fréquence et l’intensité d’agression au sein de groupes de tailles diverses, et ce, au moyen de l’échantillonnage centré de 170 caribous (64 mâles et 106 femelles) sur l’île Adak de l’archipel des Aléoutiennes, en Alaska. Les mâles des groupes du même sexe et des groupes mixtes, et les femelles de groupes mixtes affichaient une plus grande fréquence d’agression que les femelles se trouvant dans des groupes du même sexe. La fréquence d’agression n’était aucunement influencée par la taille du groupe. L’intensité d’agression des mâles était plus grande chez le mâle que chez la femelle. L’agression fréquente dans les groupes mixtes est probablement représentative de la plus faible tolérance des mâles à la présence d’animaux à proximité. Les femelles caribou étaient moins agressives et plus grégaires que les mâles, à l’instar d’autres espèces de cervidés polygynes

Simulating range-wide population and breeding habitat dynamics for an endangered woodland warbler in the face of uncertainty

Population viability analyses provide a quantitative approach that seeks to predict the possible future status of a species of interest under different scenarios and, therefore, can be important components of large-scale species’ conservation programs. We created a model and simulated range-wide population and breeding habitat dynamics for an endangered woodland warbler, the golden-cheeked warbler (Setophaga chrysoparia). Habitat-transition probabilities were estimated across the warbler's breeding range by combining National Land Cover Database imagery with multistate modeling. Using these estimates, along with recently published demographic estimates, we examined if the species can remain viable into the future given the current conditions. Lastly, we evaluated if protecting a greater amount of habitat would increase the number of warblers that can be supported in the future by systematically increasing the amount of protected habitat and comparing the estimated terminal carrying capacity at the end of 50 years of simulated habitat change. The estimated habitat-transition probabilities supported the hypothesis that habitat transitions are unidirectional, whereby habitat is more likely to diminish than regenerate. The model results indicated population viability could be achieved under current conditions, depending on dispersal. However, there is considerable uncertainty associated with the population projections due to parametric uncertainty. Model results suggested that increasing the amount of protected lands would have a substantial impact on terminal carrying capacities at the end of a 50-year simulation. Notably, this study identifies the need for collecting the data required to estimate demographic parameters in relation to changes in habitat metrics and population density in multiple regions, and highlights the importance of establishing a common definition of what constitutes protected habitat, what management goals are suitable within those protected areas, and a standard operating procedure to identify areas of priority for habitat conservation efforts. Therefore, we suggest future efforts focus on these aspects of golden-cheeked warbler conservation and ecology.Keywords: Setophaga chrysoparia, Habitat conservation, Habitat dynamics, Extinction risk, Population dynamics, Multistate mode

Elk forage response to prescribed fire in Boyes meadow, Prairie Creek Redwoods State Park, California

Prescribed fire should increase plant and forage biomass for herbivores in meadows, but the response is likely to be influenced by environmental conditions. Across 15 years prescribed fires occurred every two to four years in September in Boyes meadow, Humboldt County, California. We measured the presence or absence of prescribed fires in September, climatic conditions one month later, Roosevelt elk (Cervus elaphus roosevelti) abundance, and the biomass of elk forage in January. From analysis of a linear mixed effects model we found that prescribed fires increased forage biomass the first January post-burn and even more so a year after the burn. Forage biomass two years post-burn decreased but was still more than three to four years post-burn. October precipitation had a positive effect on forage biomass but we detected no influence from low temperature in October or elk abundance. Given that prescribed fire increased elk forage biomass two years later, continuing to burn Boyes meadow on a three to four year rotation is suggested

Hunter-effort-harvest-size relationships among hunt types of white-tailed deer

Information on hunter-effort-harvest-size relationships relevant to managing and monitoring hunted populations with multiple hunt types has not been examined in detail. We estimated harvest size from hunter effort in 6 types of hunts for white-tailed deer (Odocoileus virginianus) and compared intercepts and slopes to assess whether harvest size differed with hunting effort. The 6 hunt types were (age-sex class of population hunted and weapons allowed) as follows: antlerless gun (shotgun, centerfire rifle), either-sex archery, either-sex gun, either-sex muzzleloader, buck-only gun, and buck-only muzzleloader. The data set was a 12-year harvest record from a hunt program in western Tennessee. We measured hunter effort by hunter days (number of hunters and days they hunted). We detected differences in intercepts but not slopes among hunt types. Hunt types with largest harvest sizes were \u3e4 times larger than hunt types with smallest harvest sizes, controlling for hunter effort. Because slopes of regressions were similar, hunter effort among hunt types can be adjusted so that a harvest size:hunter effort ratio can be used to track relative deer population change

Male group size, female distribution and changes in sexual segregation by Roosevelt elk

<div><p>Sexual segregation, or the differential use of space by males and females, is hypothesized to be a function of body size dimorphism. Sexual segregation can also manifest at small (social segregation) and large (habitat segregation) spatial scales for a variety of reasons. Furthermore, the connection between small- and large-scale sexual segregation has rarely been addressed. We studied a population of Roosevelt elk (<i>Cervus elaphus roosevelti</i>) across 21 years in north coastal California, USA, to assess small- and large-scale sexual segregation in winter. We hypothesized that male group size would associate with small-scale segregation and that a change in female distribution would associate with large-scale segregation. Variation in forage biomass might also be coupled to small and large-scale sexual segregation. Our findings were consistent with male group size associating with small-scale segregation and a change in female distribution associating with large-scale segregation. Females appeared to avoid large groups comprised of socially dominant males. Males appeared to occupy a habitat vacated by females because of a wider forage niche, greater tolerance to lethal risks, and, perhaps, to reduce encounters with other elk. Sexual segregation at both spatial scales was a poor predictor of forage biomass. Size dimorphism was coupled to change in sexual segregation at small and large spatial scales. Small scale segregation can seemingly manifest when all forage habitat is occupied by females and large scale segregation might happen when some forage habitat is not occupied by females.</p></div

Abundances of the total population, female (included juveniles and sub-adult males), and adult male Roosevelt elk (<i>Cervus elaphus roosevelti</i>) in Prairie Creek Drainage, Redwood National and State Parks, California, USA, from 1997 to 2017.

<p>Percentages of females and males encountered in the Davison meadow complex are presented by the respective female and male lines.</p

Aerial photograph of the two meadow complexes in the Prairie Creek Drainage in Redwood National and State Parks.

<p>Visible to the south and east of Boyes meadow is U.S. Hwy 101.</p

Estimated means and 1 standard error bars of per ha and per capita (total forage biomass^. total elk abundance^-1) forage biomass from 2005 to 2017 in the two meadow complexes in the Prairie Creek Drainage, Humboldt County, California, USA.

<p>Estimated means and 1 standard error bars of per ha and per capita (total forage biomass^. total elk abundance^-1) forage biomass from 2005 to 2017 in the two meadow complexes in the Prairie Creek Drainage, Humboldt County, California, USA.</p

Group and meadow complex SSASs, or the sexual segregation and aggregation statistics, (solid, black line and diamonds) for Roosevelt elk (<i>Cervus elaphus roosevelti</i>) from 1997 to 2017 in Prairie Creek Drainage, Humboldt County, California, USA.

<p>The gray 95% confidence band indicates when males and females were randomly associated whereas SSAS values above the 95% confidence band indicate sexual segregation and SSAS values blow the band indicate sexual aggregation. In each year, there were 17–59 groups or solitary elk encountered.</p