Evaluation of three remote camera systems for detecting mammals and birds

Automated camera systems have widespread application in wildlife studies and their use is increasing (Kucera & Barrett 1993; Cutler & Swann 1999; Swann et al. 2004; Parker et al. 2008). Among other applications, they have been used to produce species inventories, estimate population sizes, study behaviour and examine the impact and activity of predators (Cutler & Swann 1999; Swann et al. 2004). Modern camera systems can operate for extended durations, are relatively non-invasive, easy to operate, portable, durable and can take good-quality images by day and night (Kucera & Barrett 1993; Peterson & Thomas 1998; Allison & Destefano 2006; Parker et al. 2008). Beyond their scientific applications, the generation of high-quality images can be useful for educational and conservation purposes (Cutler & Swann 1999). The two most common types of systems currently used in ecological research are passive and active infrared (IR) systems (Cutler & Swann 1999; Parker et al. 2008). An older form of remote photography is video which captures a continuous record of activity at a focal site (Stewart et al.1997; King et al. 2001). Camera systems have certain limitations and biases (Swann et al. 2004), yet these have not been well studied. Refinement of the use of camera systems is required to fully realize their value (Towerton et al. 2008). Here, we describe a comparison of detection rates of mammals and birds by passive and active IR camera systems, using a video system to benchmark detection rates.

Many routes lead to Rome : potential causes for the multi-route migration system of Red Knots, Calidris canutus islandica

Migrants, such as birds or representatives of other taxa, usually make use of several stopover sites to cover the distance between their site of origin and destination. Potentially, multiple routes exist, but often little is known about the causes and consequences of alternative migration routes. Apart from their geographical distribution, the suitability of potential sites might play an important role in the animals’ decisions for a particular itinerary. We used an optimal-migration model to test three nonmutually exclusive hypotheses leading to variations in the spring migration routes of a subspecies of Red Knot, Calidris canutus islandica, which migrates from wintering grounds in Western Europe to breeding grounds in Greenland and the Canadian Arctic: the breeding location hypothesis, the energy budget hypothesis, and the predation risk hypothesis. Varying only breeding location, the model predicted that birds breeding in the Canadian Arctic and on West Greenland stop over on Iceland, whereas birds breeding in East and Northeast Greenland migrate via northern Norway, a prediction that is supported by empirical findings. Energy budgets on stopover sites had a strong influence on the choice of route and staging times. Varying foraging-intensity and mass-dependent predation risk prompted the birds to use less risky sites, if possible. The effect of simultaneous changes in the energy budget and predation risk strongly depended on the site where these occurred. Our findings provide potential explanations for the observations that C. canutus islandica uses a diverse array of migration routes. Scrutinizing the three alternative driving forces for the choice of migratory routes awaits further, specific data collection in rapidly developing fields of research (e.g., predation risk assessment, GPS tracking). Generally, the type of modeling presented here may not only highlight alternative explanations, but also direct follow-up empirical research.

Compensatory growth in an aquatic plant mediates exploitative competition between seasonally tied herbivores

The degree to which vertebrate herbivores exploitatively compete for the same food plant may depend on the level of compensatory plant growth. Such compensation is higher when there is reduced density-dependent competition in plants after herbivore damage. Whether there is relief from competition may largely be determined by the life-history stage of plants under herbivory. Such stage-specific compensation may apply to seasonal herbivory on the clonal aquatic plant sago pondweed (Potamogeton pectinatus L.). It winters in sediments of shallow lakes as tubers that are foraged upon by Bewick's Swans (Cygnus columbianus bewickii Yarrell), whereas aboveground biomass in summer is mostly consumed by ducks, coots, and Mute Swans. Here, tuber predation may be compensated due to diminished negative density dependence in the next growth season. However, we expected lower compensation to summer herbivory by waterfowl and fish as density of aboveground biomass in summer is closely related to photosynthetic carbon fixation. In a factorial exclosure study we simultaneously investigated (1) the effect of summer herbivory on aboveground biomass and autumn tuber biomass and (2) the effect of tuber predation in autumn on aboveground biomass and tuber biomass a year later. Summer herbivory strongly influenced belowground tuber biomass in autumn, limiting food availability to Bewick's Swans. In contrast, tuber predation in autumn by Bewick's Swans had a limited and variable effect on P. pectinatus biomass in the following growth season. Whereas relief from negative density dependence largely eliminates effects of belowground herbivory by swans, aboveground herbivory in summer limits both above- and belowground plant biomass. Hence, there was an asymmetry in exploitative competition, with herbivores in summer reducing food availability for belowground herbivores in autumn, but not the other way around.

Modelling behavioural and fitness consequences of disturbance for geese along their spring flyway

1. For migratory birds the implications of environmental change may be difficult to predict because they use multiple sites during their annual cycle. Moreover, the migrants’ use of these sites may be interdependent. Along the flyway of the Svalbard pink-footed goose Anser brachyrhynchus population, Norwegian farmers use organized scaring to minimize goose use of their grasslands in spring. We assessed the consequences of this practice for regional site use of pink-footed geese along their spring migration route.

2. We used dynamic programming to find the sequence of migratory decisions that maximizes the fitness of female geese during spring migration, assuming scaring impinges on both food-intake rates and predation risk. The parameterization of the model was based on data gathered from individually marked pink-footed geese between 1991 and 2003.

3. The effect of scaring in terms of fitness and site use was most noticeable regarding food-intake rate. Scaring resulted in a redistribution of geese along the flyway. Furthermore, the outcomes of the modelling exercises were highly dependent on whether or not the geese were omniscient or naive: at moderate scaring levels naive geese were predicted to succumb.

4. On a qualitative basis there was good correspondence between the predictions from the model and the empirical evidence gathered to date.

5. Synthesis and applications. Besides highlighting the importance of learning and changing behaviour in an adaptive fashion, our modelling exercise indicated the potential vulnerability of the geese to abrupt environmental change. In addition, the exercise emphasized the interdependence of site use along the migratory flyway. The model supports the necessity for an integrated flyway management approach. In Norway, discussion is ongoing about the future management of the spring conflict between farming interests and geese. Farmers in north and mid-Norway have announced that they will expand the scaring campaign if a long-term solution, including a compensation scheme, is not forthcoming. If scaring on such a large scale is implemented abruptly, it may have severe consequences for the population: management of both the scaring intensity and its geographical extent is urgently required.

A new approach to determining environmental flow requirements : sustaining the natural values of floodplains of the southern Murray-Darling Basin

Large overbank flood events play an important role in maintaining largescale ecological processes and connectivity along and across the floodplains and between the rivers and their floodplains in the southern Murray-Darling Basin. However, the regulation of rivers means that extensive overbank flooding can only occur in the rare circumstance of extreme flood events. Recent environmental water allocations have focussed on the largest floodplain blocks (‘icon’ sites) and a small set of specific values (e.g. colonial nesting waterbirds), as well as on trialling fine-scale manipulation of infrastructure (e.g. pumping) to water relatively small areas. There has been no comprehensive systematic assessment of the entire floodplain and its wider set of flood-dependent natural assets (such as ecosystems and species; herein referred to as ‘natural values’) to maximise the effectiveness of environmental water use and to catalogue values likely to be lost. This paper describes an assessment of some 220 000 ha found to support flood-dependent natural values in Victoria. We mapped the geographic distribution and estimated components of the flooding requirements (natural flooding frequency, and maximum period without flooding and minimum duration of each flooding event before significant deterioration) for each natural value. Using an example of one stretch of the River Murray, we show how the resultant spatial data can be used with floodplain inundation modelling to compare the outcomes of real or planned environmental watering events; potentially providing tools for management agencies to conserve a wider range of floodplain values than is currently the case. That is, water managers and the public can see what ecosystems and threatened species are intended to be maintained by environmental watering and what values are intended to be abandoned across the whole floodplain, rather than just seeing the small subset of values and ‘icon’ sites that are intended to be maintained. Examples are provided to illustrate how information about the location, water requirements and extent covered by potential floods for specific values can be used to build adaptive watering strategies for areas as large as the whole floodplain.

Large-herbivore distribution and abundance : intra-and interspecific niche variation in the tropics

Determining the biological and environmental factors that limit the distribution and abundance of organisms is central to our understanding of the niche concept and crucial for predicting how species may respond to large-scale environmental change, such as global warming. However, detailed ecological information for the majority of species has been collected only at a local scale, and insufficient consideration has been given to geographical variation in intraspecific niche requirements. To evaluate the influence of environmental and biological factors on patterns of species distribution and abundance, we conducted a detailed, broadscale study across the tropical savannas of northern Australia on the ecology of three large, sympatric marsupial herbivores (family Macropodidae): the antilopine wallaroo (Macropus antilopinus), common wallaroo (M. robustus), and eastern grey kangaroo (M. giganteus). Using information on species abundance, climate, fire history, habitat, and resource availability, we constructed species' habitat models varying from the level of the complete distribution to smaller regional areas. Multiple factors affected macropod abundance, and the importance of these factors was dependent on the spatial scale of analyses. Fire regimes, water availability, geology, and soil type and climate were most important at the large scale, whereas aspects of habitat structure and interspecific species abundance were important at smaller scales. The distribution and abundance of eastern grey kangaroos and common wallaroos were strongly influenced by climate. Our results suggest that interspecific competition between antilopine wallaroos and eastern grey kangaroos may occur. The antilopine wallaroo and eastern grey kangaroo (grazers) preferred more nutrient-rich soils than the common wallaroo (grazer/browser), which we relate to differences in feeding modes. The abundance of antilopine wallaroos was higher on sites that were burned, whereas the abundance of common wallaroos was higher on unburned sites. Future climate change predicted for Australia has the capacity to seriously affect the abundance and conservation of macropod species in tropical savannas. The results of our models suggest that, in particular, the effects of changing climatic conditions on fire regimes, habitat structure, and water availability may lead to species declines and marked changes in macropod communities.

Insights into the biodiversity and social benchmarking components of the Northern Australian fire management and carbon abatement programmes

Much of northern Australia’s tropical savannas are subject to annual intense and extensive late dry season wildfires, much of this occurring on Aboriginal land. Based on the successful West Arnhem Land Fire Abatement (WALFA) model, which has resulted in significantly reduced greenhouse gas emissions, fire abatement programmes are planned for other significant regions of northern Australia. This study offers an introduction to the ideas behind a proposed environmental and social benchmarking project that aims to evaluate the potential benefits of expanding the fire abatement program in northern Australia, under the leadership of NAILSMA and its partners. Gaining a better understanding of the biodiversity, social and cultural outcomes of these fire abatement activities is an important component of demonstrating multiple benefits of these programmes. We emphasize the role of both biodiversity and cultural mapping to establish benchmarks and baseline states, with the involvement of Indigenous communities being a key element to optimize social and biodiversity benefits. Consultation with Traditional Owners and ranger groups to establish an agreed set of targets, indicators and sampling protocols and methodologies are critical component of this process. Examples of preliminary work to date are provided.

Habitat use throughout migration : linking individual consistency, prior breeding success and future breeding potential

1. Habitat use can influence individual performance in a wide range of animals, either immediately or through carry-over effects in subsequent seasons. Given that many animal species also show consistent individual differences in reproductive success, it seems plausible that individuals may have consistent patterns of habitat use representing individual specializations, with concomitant fitness consequences.

2. Stable-carbon isotope ratios from a range of tissues were used to discern individual consistency in habitat use along a terrestrial–aquatic gradient in a long-distance migrant, the Bewick’s swan (Cygnus columbianus bewickii). These individual specialisations represented <15% of the isotopic breadth of the population for the majority of individuals and were seen to persist throughout autumn migration and overwintering until aquatic habitats were no longer available.

3. Individual foraging specialisations were then used to demonstrate two consecutive carry-over effects associated with macroscale habitat segregation: consequences of breeding season processes for autumn habitat use; and consequences of autumn habitat use for future reproductive success. Adults that were successful breeders in the year of capture used terrestrial habitats significantly more than adults that were not successful, revealing a substantial cost of reproduction and extended parental care. Use of aquatic habitats during autumn was, however, associated with increased body condition prior to spring migration; and increased subsequent breeding success in adults that had been unsuccessful the year before. Yet adults that were successful breeders in the year of capture remained the most likely to be successful the following year, despite their use of terrestrial habitats.

4. Our results uniquely demonstrate not only individual foraging specializations throughout the migration period, but also that processes during breeding and autumn migration, mediated by individual consistency, may play a fundamental role in the population dynamics of long-distance migrants. These findings, therefore, highlight the importance of long-term consistency to our understanding of habitat function, interindividual differences in fitness, population dynamics and the evolution of migratory strategies.

Effects of time since fire on birds : how informative are generalized fire response curves for conservation management?

Fire is both a widespread natural disturbance that affects the distribution of species and a tool that can be used to manage habitats for species. Knowledge of temporal changes in the occurrence of species after fire is essential for conservation management in fire-prone environments. Two key issues are: whether postfire responses of species are idiosyncratic or if multiple species show a limited number of similar responses; and whether such responses to time since fire can predict the occurrence of species across broad spatial scales. We examined the response of bird species to time since fire in semiarid shrubland in southeastern Australia using data from surveys at 499 sites representing a 100-year chronosequence. We used nonlinear regression to model the probability of occurrence of 30 species with time since fire in two vegetation types, and compared species' responses with generalized response shapes from the literature. The occurrence of 16 species was significantly influenced by time since fire: they displayed six main responses consistent with generalized response shapes. Of these 16 species, 15 occurred more frequently in mid- or later-successional vegetation (>20 years since fire), and only one species occurred more often in early succession (<5 years since fire). The models had reasonable predictive ability for eight species, some predictive ability for seven species, and were little better than random for one species. Bird species displayed a limited range of responses to time since fire; thus a small set of fire ages should allow the provision of habitat for most species. Postfire successional changes extend for decades and management of the age class distribution of vegetation will need to reflect this timescale. Response curves revealed important seral stages for species and highlighted the importance of mid- to late-successional vegetation (>20 years). Although time since fire clearly influences the distribution of numerous bird species, predictive models of the spatial distribution of species in fire-prone landscapes need to incorporate other factors in addition to time since fire.

Genes and song : genetic and social connections in fragmented habitat in a woodland bird with limited dispersal

Understanding the processes leading to population declines in fragmented landscapes is essential for successful conservation management. However, isolating the influence of disparate processes, and dispersal in particular, is challenging. The Grey Shrike-thrush, Colluricincla harmonica, is a sedentary woodland-dependent songbird, with learned vocalizations whose incidence in suitable habitat patches falls disproportionally with decline in tree cover in the landscape. Although it has been suggested that gaps in tree cover might act as barriers to its dispersal, the species remains in many remnants of native vegetation in agricultural landscapes, suggesting that it may have responded to habitat removal and fragmentation by maintaining or even increasing dispersal distances. We quantified population connectivity of the Grey Shrike-thrush in a system fragmented over more than 120 years using genetic (microsatellites) and acoustic (song types) data. First, we tested for population genetic and acoustic structure at regional and local scales in search of barriers to dispersal or gene flow and signals of local spatial structuring indicative of restricted dispersal or localized acoustic similarity. Then we tested for effects of habitat loss and fragmentation on genetic and acoustic connectivity by fitting alternative models of mobility (isolation-by-distance [the null model] and reduced and increased movement models) across treeless vs. treed areas. Birds within 5 km of each other had more similar genotypes and song types than those farther away, suggesting that dispersal and song matching are limited in the region. Despite restricted dispersal detected for females (but not males), populations appeared to be connected by gene flow and displayed some cultural (acoustic) connectivity across the region. Fragmentation did not appear to impact greatly the dispersal of the Grey Shrike-thrush: none of the mobility models fit the genetic distances of males, whereas for females, an isolation-by-distance model could not be rejected in favor of the models of reduced or increased movement through treeless gaps. However, dissimilarities of the song types were more consistent with the model of reduced cultural connectivity through treeless areas, suggesting that fragmentation impedes song type sharing in the Grey Shrike-thrush. Our paper demonstrates that habitat fragmentation hinders important population processes in an Australian woodland bird even though its dispersal is not detectably impacted.

How the ladybird got its spots : effects of resource limitation on the honesty of aposematic signals

Prey species often possess defences (e.g. toxins) coupled with warning signals (i.e. aposematism). There is growing evidence that the expression of aposematic signals often varies within species and correlates with the strength of chemical defences. This has led to the speculation that such signals may be 'honest', with signal reliability ensured by the costliness of producing or maintaining aposematic traits. We reared larval seven-spot ladybirds (Coccinella septempunctata) on a Low or High aphid diet and measured the effects on warning signal expression (elytral carotenoid pigmentation, conspicuousness, spot size), levels of defensive alkaloids (precoccinelline, coccinelline), and relationships between these traits. High-diet individuals had greater total precoccinelline levels, and elytra carotenoid concentrations at adulthood which was detectable to a typical avian predator. However, larval diet did not significantly affect adult body mass or size, spot size or coccinelline levels. Elytra carotenoid concentrations correlated positively with total precoccinelline levels in both diet groups and sexes. However, the relationship between elytra carotenoid concentrations and total levels of coccinelline depended on sex: in both diet groups, elytra carotenoids and coccinelline levels were positively correlated in females, but negatively correlated in males. Spot size and coccinelline levels correlated positively in Low-diet individuals, but negatively in High-diet individuals. These results point to physiological linkages between components of aposematism, which are modulated by resource (i.e. food) availability and affect the honesty of signals. Developmental diet, but also sex, influenced the relationships between signals and toxin levels. Ladybirds are sexually size dimorphic, and thus in comparison with males, females may be more susceptible to resource limitation and more likely to be honest signallers. © 2012 The Authors. Functional Ecology © 2012 British Ecological Society.

Density-dependent mortality is mediated by foraging activity for prey fish in whole-lake experiments

1. Whereas the effects of density-dependent growth and survival on population dynamics are well-known, mechanisms that give rise to density dependence in animal populations are not well understood. We tested the hypothesis that the trade-off between growth and mortality rates is mediated by foraging activity and habitat use. Thus, if depletion of food by prey is density-dependent, and leads to greater foraging activity and risky habitat use, then visibility and encounter rates with predators must also increase.

2. We tested this hypothesis by experimentally manipulating the density of young rainbow trout (Oncorhynchus mykiss) at risk of cannibalism, in a replicated single-factor experiment using eight small lakes, during an entire growing season.

3. We found no evidence for density-dependent depletion of daphnid food in the near-shore refuge where most age-0 trout resided. Nonetheless, the proportion of time spent moving by individual age-0 trout, the proportion of individuals continuously active, and use of deeper habitats was greater in high density populations than in low density populations. Differences in food abundance among lakes had no effect on measures of activity or habitat use.

4. Mortality of age-0 trout over the growing season was higher in high density populations, and in lakes with lower daphnid food abundance. Therefore, population-level mortality of age-0 trout is linked to greater activity and use of risky habitats by individuals at high densities. We suspect that food resources were depleted at small spatial and temporal scales not detected by our plankton sampling in the high density treatment, because food-dependent activity and habitat use by age-0 trout occurs in our lakes when food abundance is experimentally manipulated

The central-place territorial model does not apply to space-use by juvenile brook charr Salvelinus fontinalis in lakes

1. Territoriality is widely accepted as the mechanism responsible for density-dependent mortality, emigration, and 'self-thinning' of populations of juvenile salmonine fishes in streams. Numerous studies have focused on territoriality exclusively in stream (lotic) environments and thus have fostered a stereotyped view of juvenile salmonines as sedentary and territorial. We term this behavioural paradigm the central-place territorial model (CPTM).

2. We tested predictions characterizing the CPTM for young-of-the-year (YOY) brook charr (Salvelinus fontinalis) in two Canadian lakes to determine if territoriality may also potentially limit space and population size of brook charr in lakes.

3. Our findings were not consistent with the CPTM. Fish in both lakes were not central-place forages. Maximum displacement distance did not increase with body length as predicted by the general salmonine model of Grant and Kramer (1990). Net displacement distanced increased with the proportion of time spent moving. Aggressive frequency was greatest for fish which spent large proportions of time moving and did not defend from a central-place.

4. Fish in both lakes were rarely aggressive, highly active, and often moved back over the same areas. However, lake fish which migrated to a tributary stream had no net displacement (central-place foraging) illustrating the immediate effects of current on foraging tactics and space-use.

5. The effect of hydrodynamic environment (flowing vs. still water) on fish behaviour needs to be explicitly considered in future models of salmonine behaviour.

From individuals to populations : prey fish risk-taking mediates mortality in whole-system experiments

Recent research suggests that the behavior of individuals under risk of predation could be a key link between individual behavior and population and community dynamics. Yet existing theory remains largely untested at large spatial and temporal scales. We manipulated food available to age-0 rainbow trout while at risk of cannibalism, in a replicated factorial whole-lake experiment, to test whether the trade-off between growth and mortality rates is mediated by foraging activity by young fish under predation risk. We found that this trade-off exists for young fish at the whole-system scale, and that food-dependent behavioral variation has large mortality consequences. In high-food lakes, age-0 trout spent less time moving, fewer individuals swam continuously, and those swimming continuously swam at slower speeds relative to those in low-food lakes. Age-0 trout also used deep, risky habitats less when food was abundant. This lower activity, combined with avoidance of risky habitats, coincided with 68% higher survival in high-food lakes. If general, this trade-off may be a key mechanism linking individual behavior to population-level processes in size-structured populations.