Animal movement in dynamic landscapes: interaction between behavioural strategies and resource distributions

Scale and landscape perception: the case of refuge use by Boreal Toads (Anaxyrus boreas boreas)

Refugia likely represent a critical resource necessary for the persistence of populations of Boreal Toads ( Anaxyrus boreas boreas (Baird and Girard, 1852)) in a given area. However, the features that define suitable refuge microsites and the extent to which the habitat surrounding refugia is exploited remains unclear. We sought to describe refuge characteristics in the context of their surroundings and to determine whether local-scale movement behaviour associated with refuge use might provide a novel perspective of landscape-level habitat selection. A pilot study suggested that refugia were selected primarily for physical structure in the form of coarse woody debris, but this was not the case. Instead, refugia provided favourable microclimates with elevated relative humidity compared with the surrounding habitat. Boreal Toads tended to forage at night within 15 m from refugia. This distance was used to calculate activity centres across toad summer home ranges. Activity centres prioritized the importance of treeless habitat overall and wetland habitat for females when compared with 50% core home ranges. This approach could be used to pinpoint critical habitat at the landscape scale, which may be of particular importance for conserving populations currently in decline.

Breaking functional connectivity into components: a novel approach using an individual-based model, and first outcomes

Landscape connectivity is a key factor determining the viability of populations in fragmented landscapes. Predicting 'functional connectivity', namely whether a patch or a landscape functions as connected from the perspective of a focal species, poses various challenges. First, empirical data on the movement behaviour of species is often scarce. Second, animal-landscape interactions are bound to yield complex patterns. Lastly, functional connectivity involves various components that are rarely assessed separately. We introduce the spatially explicit, individual-based model FunCon as means to distinguish between components of functional connectivity and to assess how each of them affects the sensitivity of species and communities to landscape structures. We then present the results of exploratory simulations over six landscapes of different fragmentation levels and across a range of hypothetical bird species that differ in their response to habitat edges. i) Our results demonstrate that estimations of functional connectivity depend not only on the response of species to edges (avoidance versus penetration into the matrix), the movement mode investigated (home range movements versus dispersal), and the way in which the matrix is being crossed (random walk versus gap crossing), but also on the choice of connectivity measure (in this case, the model output examined). ii) We further show a strong effect of the mortality scenario applied, indicating that movement decisions that do not fully match the mortality risks are likely to reduce connectivity and enhance sensitivity to fragmentation. iii) Despite these complexities, some consistent patterns emerged. For instance, the ranking order of landscapes in terms of functional connectivity was mostly consistent across the entire range of hypothetical species, indicating that simple landscape indices can potentially serve as valuable surrogates for functional connectivity. Yet such simplifications must be carefully evaluated in terms of the components of functional connectivity they actually predict.

Marine reserves: fish life history and ecological traits matter

Marine reserves are assumed to protect a wide range of species from deleterious effects stemming from exploitation. However, some species, due to their ecological characteristics, may not respond positively to protection. Very little is known about the effects of life history and ecological traits (e.g., mobility, growth, and habitat) on responses of fish species to marine reserves. Using 40 data sets from 12 European marine reserves, we show that there is significant variation in the response of different species of fish to protection and that this heterogeneity can be explained, in part, by differences in their traits. Densities of targeted size-classes of commercial species were greater in protected than unprotected areas. This effect of protection increased as the maximum body size of the targeted species increased, and it was greater for species that were not obligate schoolers. However, contrary to previous theoretical findings, even mobile species with wide home ranges benefited from protection: the effect of protection was at least as strong for mobile species as it was for sedentary ones. Noncommercial bycatch and unexploited species rarely responded to protection, and when they did (in the case of unexploited bentho-pelagic species), they exhibited the opposite response: their densities were lower inside reserves. The use of marine reserves for marine conservation and fisheries management implies that they should ensure protection for a wide range of species with different life-history and ecological traits. Our results suggest this is not the case, and instead that effects vary with economic value, body size, habitat, depth range, and schooling behavior.

Woodland bird declines in the Murray–Darling Basin: are there links with floodplain change?

Woodland bird population declines in Australia have been attributed to various factors including habitat loss, fragmentation, and degradation. However, the influence of altered water availability in the landscape upon woodland bird populations has not been examined, particularly in terms of changes in flood regimes and subsequent loss of floodplain productivity. In this review, we examine the importance to woodland birds of floodplains, floods, and associated vegetation communities, highlighting potential links between declining water availability, habitat degradation, and bird populations. Floodplain woodlands and forests may be important refuges for woodland bird populations because (1) floodplain woodlands and forests comprise some of the largest and most continuous vegetation remnants in south-east Australia; and (2) floods intermittently supply water, sediment and nutrients that drive greater primary and secondary productivity than found in woodlands not subject to flooding. However, floodplains in south-east Australia have been subject to substantial flow regime change, driven predominantly by dams and irrigation water use. Consequently, habitat quality for woodland birds has been degraded, potentially exacerbating population declines. We suggest that despite such change, floodplain communities and their requisite floods remain of great importance for the persistence, productivity and diversity of woodland birds in Australian drylands. We hypothesise that (1) the influence of flooding upon primary and secondary productivity in floodplain and riparian zones is a key driver of resident bird populations, and a key determinant of nomadic/migratory bird use of a site; (2) alterations in flooding and consequent changes in productivity and condition of floodplain vegetation have contributed to observed declines in resident woodland birds in Australian drylands; and (3) the influence of flooding upon productivity extends beyond local populations of floodplain residents to non-floodplain populations via dispersal, and that floodplain woodlands often act as a source population for surrounding non-floodplain woodlands. We make several testable predictions regarding these hypotheses.