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In the context of remarkable increases in many deer populations observed in temperate forests, it is critical to better understand the processes sustaining abundant populations despite dramatic declines in the vegetation they feed on. When natural predation and hunting levels are too low to control deer populations, a resource-driven negative feedback is expected. Such a feedback assumes that the remaining resources do not match the energy requirements of a current herbivore population, thereby limiting herbivore abundance. Here we take advantage of a well-documented, long-term study of abundant predator-free populations of black-tailed deer Odocoileus hemionus sitkensis on the Haida Gwaii archipelago (Canada) to assess the ability of a heavily browsed forest habitat to sustain abundant deer populations. For two deer populations, we: 1) compared the energy provided by various resource pools to the energy required by deer; and 2) identified what components of the environment contributed most to support them. Qualitatively, our results are robust to the many assumptions and uncertainties and identify the resources currently available that allow these abundant deer populations to meet their energy needs despite the apparent paucity in resources. Resources are provided by a flux of hardly visible plant tissue produced by perennial species highly tolerant of herbivory and able to survive via underground structures (e.g. rhizomes), and by subsidies provided by canopy trees or by plants in refuges (i.e. litterfall and seed bank). We discuss the possibility of a resource-driven feedback that may ultimately occur in the long term as a result of changes in recruitment, productivity and fertility of plants. The possible lack of resource-driven feedback in the short or medium term should be considered by managers when assessing the need for active deer population control in situations without carnivores or hunting.
This study investigated the potential use of diversionary feeding and behavior-contingent sonic deterrents to mitigate the herbivory impacts of capybaras Hydrochoerus hydrochaeris on a riparian forest restoration site in the watershed of the Velhas River, the main tributary of the S. Francisco River in southeastern Brazil. Paspalum notatum, popularly known as batatais or bahia grass, was chosen as a diversionary food candidate and motion-activated sonic alarms were used as deterrents. A field experiment was conducted to compare the plant cover and the damage incidence in a fenced-off control on open plots with and without sonic deterrents. In these plots, P. notatum was cultivated alongside other restoration species of interest. Capybaras distinctly preferred P. notatum, which suffered 8.14-fold greater damage than other species and suffered coverage losses of up to 40% outside of the control plots, whereas the remaining species showed no difference from the control. The sonic deterrents did not influence the soil cover by any of the species, but did mitigate the damage to P. notatum independently of time. The damage was 93% more prevalent in the plots without deterrents. This success was partial, however, because damage also occurred in the presence of the deterrents. P. notatum was efficient at attracting and concentrating the interest of capybaras and therefore showed promise as a cover crop to protect other species of interest. Overall, the results of this study suggest that P. notatum is more efficient than electronic deterrents to protect a forest under restoration process against capybara damage.
Carnivore populations are increasingly confined to reserves surrounded by anthropogenic development. The boundaries of ecological islands are risky because of habitat loss and human—carnivore conflict. From snow track survey data collected over a 5-winter period we developed a population-level resource selection function for Canada lynx Lynxcanadensis in Riding Mountain National Park, Canada. This park has been characterized as an ‘ecological island situated amidst a sea of agricultural land’ and while lynx are protected within the park, they are subject to harvest outside of the park. Winter resource selection of lynx increased with higher elevation and in highly suitable habitat for snowshoe hare Lepus americanus and decreased in habitat with greater proportions of agriculture and grasslands, both of which are common along the edge of the park. Habitat with medium to high relative probabilities of lynx occurrence tended to be distributed in the interior of the park. However, the highest relative probability of lynx occurrence was associated with habitat near the southeast border of the park in close proximity to a human community and a lake where snowmobiling, skiing, and snowshoeing are common recreational pursuits. We attribute this relationship to a 25-year old fire which presently created successional habitat highly suitable for snowshoe hare and correspondingly for lynx in this area. Our results suggest that Canada lynx occurrence tends to be associated with habitat that is highly suitable for their primary prey even if that habitat is located near to sources of human recreational activity.
Hedgehogs are one of the most common mammalian road fatalities in Europe. Between April 2008 and November 2010, two stretches of road measuring 227 km (Cork City to Caherlistrane, Co. Galway) and 32.5 km (Cork City to Bandon, Co. Cork) respectively were surveyed for hedgehog road kill. In addition to the sightings of road kill on the two stretches of road, a further 135 carcasses were collected over the study period from throughout Ireland and the sex and age group were recorded. Over the three years, a total of 50 430 km were surveyed and 133 hedgehog fatalities were observed between the two surveyed roads. The number of hedgehog road kill per km in the current study was low when compared to countries such as Belgium, Poland and New Zealand. It is suggested that this may be a consequence of hedgehogs having a greater opportunity to encounter larger busier roads in other countries. Over the three years, the majority of the 133 carcasses sighted were located beside pasture, which was the most prominent habitat along both routes. Arable land was the only habitat used in a greater proportion than what was available. K-function analysis detected clustering along the surveyed roads, with fatalities clustering annually at several locations. This would suggest that hedgehogs may use specific crossing points which would be important for the implementation of management strategies and underpass construction. Of the 135 hedgehog carcasses collected from throughout Ireland there was significantly more males than females collected, with peaks in male deaths occurring in May and June. Female deaths only outnumbered males in August, with further peaks in female deaths observed in June and July. It is suggested that these peaks are related to the breeding season (adults) and dispersal/ exploration following independence (juveniles).
The landscape in southern Iberia has, over the last four decades, altered as a result of the land abandonment, while the abundance of wild boar Sus scrofa and red deer Cervus elaphus has simultaneously increased, and some key prey species such as the European rabbit Oryctolagus cuniculus have declined. In this work we explore: 1) the relationships between big game species (red deer and wild boar) and rabbit abundance, and 2) whether these relationships could have effects on food quality (total nitrogen available in the pasture and percentage of leguminosae) and food availability of (herbaceous cover). We therefore selected nine big game estates with a range of abundance as regards ungulates and similar Mediterranean habitat. Wild boar abundance was statistically negative in relation to rabbit abundance, while no significant statistical relationships between rabbit abundance and habitat structure and forage quality were evidenced. However, wild boar abundance, but not that of red deer, was negatively associated with leguminosae cover, and the percentage of surface rooted by wild boar was negatively associated with the percentage of herbaceous cover. Overall, our results suggest that the abundance of wild boar is negatively related to that of rabbits, and could have a negative effects on rabbit abundances by food competition as a result of: 1) a decrease in herbaceous coverage and leguminosae in the pasture and 2) an increase in the total percentage of soil disturbed as a result of rooting.
The domestic cat Felis silvestris catus is considered a potential threat to the native fauna of regions it populates, particularly when it has free access to these areas. Although this problem is known in Brazil, little is known regarding the effects of this species on natural areas. This study aimed to obtain information concerning the diet of domestic cats by identifying the main items found in fecal samples from domestic cats. In addition, the effects of seasonality on the diet were examined, as it has been hypothesized that seasonal variation of food items has little influence of the diet of the domestic cat. These semi-domiciled cats are thought to face a constant and continuous supply food offered by their owners throughout the year. Feces were collected in a remnant fragment of an Atlantic Forest located south of the municipality of Ilha Comprida — SP, Brazil. These samples provided important information regarding the dietary ecology and predation behavior of this species in endangered forest areas. The results of the scat content analyses demonstrated that domestic cats inserted in this biome presented a generalist and opportunist diet with little seasonal variation, even when receiving food from their owners. The most frequently consumed groups of prey were insects (20.8%) followed by mammals (13.9%) and birds (4.0%). Although the cat is not the only factor that impacts the species of the region, management programs need to be established in conjunction with the local community with the aim of minimizing the pressure exerted by these animals on the native fauna.
Manipulating hunting season length is often used as a population management tool but the effects of these changes on total harvest have rarely been studied. We modelled relative changes in national annual bag size as a function of relative change in hunting season length in 63 cases involving 28 species in Denmark (1957–2007). The duration of the hunting season, initially lasting 30–365 days, was modified to 39–204% of the former length. The undifferentiated effect of season length change on bag size change (all 63 cases) was not statistically significant (b = 0.16, 95%CI: -0.04–0.36), with a 10% (95%CI: -3–22%) predicted decrease in bag size upon a 50% reduction of season length. However, the functional relationship between the relative change in bag size and the change in season length differed between sedentary and non-sedentary species and interacted with the motivation behind changing season length (population management/ethical/other). In non-sedentary species, changes in bag size correlated positively with changes in season length (overall response: b = 0.54, 95%CI: 0.14–0.95): reducing the hunting season to 50% of its initial length would on average result in a 31% reduction (95% CI: 9–48%) of total bag size. This overall effect interacted with the motivation for season length changes, being strongest for ‘other reasons’ (mainly harmonization of hunting periods for related species) but was absent when seasons were changed for reasons of ‘population management’. In sedentary species, changes in season length had no effect on bag size. Our results suggest that manipulating hunting seasons of duration ≥ 1 month by less than 50% is generally inefficient as a means of predictably changing harvest rates. This may be because recreational hunters either invest a fixed effort or aim for a specific yield within a given season, neither strategy being affected by changes in hunting seasons.
The East African Rift Valley Lakes Bogoria and Nakuru sometimes host around 75% of the world population of lesser flamingos Phoeniconaias minor. In this area, mysterious flamingo die-offs have occupied researchers for four decades. Recently, cyanobacterial toxins came into the fore as a possible explanation for mass mortalities because the main food source of lesser flamingos is the cyanobacterium Arthrospira fusiformis. We took weekly samples from July 2008 to November 2009 from Lakes Nakuru and Bogoria and analyzed them by high performance liquid chromatography for microcystins. Monthly, samples were cross-checked using protein phosphatase inhibition assays with lower detection limits and additionally screened for polar toxins. During our study period, three flamingo die-offs occurred at L. Bogoria and we were able to analyze tissues of 20 carcasses collected at the shoreline. No cyanotoxins were detected either in plankton samples or in flamingo tissues. Accordingly, other reasons such as food composition or bird diseases played a key role in the observed flamingo die-offs.
The Cape fox Vulpes chama is one of the least studied Vulpes species, and little is known about their diet. By analyzing contents of scats, we determined the seasonal diet of Cape foxes on Benfontein Game Farm (BGF) in South Africa, and determined the biomass and number of rodents consumed. We also determined the diet of Cape foxes on a nearby private livestock ranch (PR) in winter when sheep were lambing. On BGF, murids were the dominant food item, and comprised 44–90% of the biomass consumed across seasons. Other major food items that were seasonally important were leporids and berries. Although arthropods were frequently consumed, they were negligible in terms of biomass consumed. On PR, sheep were found in 19% of scats, but in relatively low amounts per scat, indicating sheep were likely scavenged rather than predated upon. On BGF, the estimated annual consumption was 3,861 rodent/fox, or about 11 rodent/day/fox. Our results indicate Cape foxes feed primarily on small rodents, and therefore Cape foxes might be beneficial to livestock and game farm owners in southern Africa.