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Context. Despite large mammals being an important component of many ecosystems, there is little information on the impacts of fire on large mammal populations.
Aims. We evaluated the effects of the large-scale high-severity ‘Black Saturday’ fires of 7 February 2009 on occupancy and abundances of an invasive large mammal, the sambar deer (Cervus unicolor), in south-eastern Australia.
Methods. The effects of the Black Saturday fires on the abundance of sambar deer were assessed using repeated annual counts of faecal pellets during 2007–11 in Kinglake National Park, which was burnt, and in Mount Buffalo National Park, which was not burnt. Pre-fire occupancy was modelled from data collected at 80 4-km2 cells using three survey methods. The same survey methods were used at 15 burnt (n = 9 sampled pre-fire) and 15 unburnt (n = 5 sampled pre-fire) cells 16–24 months after Black Saturday. Because multiple surveys were performed in each cell, we used a Bayesian state–space site-occupancy model to partition changes in the probability of occupancy from changes in the probability of detection.
Key results. Counts of sambar deer pellets increased linearly during 2007–11 in the unburnt Mount Buffalo National Park. Pellet counts also increased linearly in Kinglake National Park from 2007 to 2008, and then decreased (to zero) following Black Saturday; pellet counts increased again in 2010 and 2011. Sambar deer occupancy was weakly reduced (from 0.99 to 0.88) in burnt cells 16–24 months after Black Saturday, but was little changed in unburnt cells (from 0.99 to 0.98).
Conclusions. We conclude that the abundance of sambar deer was substantially reduced by the large-scale high-severity Black Saturday fires, but that most burnt habitat was reoccupied 16–24 months later.
Implications. There is concern about the negative impacts of invasive sambar deer on native biodiversity, particularly immediately post-fire. Our study suggests that it takes at least 8 months before sambar deer recolonise areas burnt by a large-scale high-severity fire; however, a risk-averse approach would be to act (e.g. by erecting fences or culling) sooner than that.
Context. Timing (mean birthdate) and synchrony (variance around that date) of births can influence survival of young and growth in ungulate populations. Some restored populations of ungulates may not adjust these life-history characteristics to environments of release sites until several years after release, which may influence success of reintroductions.
Aims. We quantified timing and synchrony of births from 2005 to 2007 in four populations of reintroduced bighorn sheep (Ovis canadensis) occupying two ecoregions (Central Basin and Range and Wasatch and Uinta Mountains) in Utah, USA, to investigate whether bighorns would adjust these life-history characteristics to environmental conditions of the two ecoregions. We also compared timing and synchrony of births for bighorns in their source herd (Antelope Island) with bighorns in an ecologically similar release site (Stansbury Mountains) during 2006 and 2007.
Methods. We relocated female bighorns to record birthdates of young, and observed groups of collared bighorns to quantify use of elevation by those ungulates. We also calculated the initiation, rate and timing of peak green-up by ecoregion, using the normalised difference vegetation index.
Key results. We quantified 274 birthdates, and although only separated by 57 km, bighorn populations occupying the Central Basin and Range Mountains gave birth an average of 29 days earlier than did those on the Wasatch and Uinta Mountains, which corresponded with the initiation of vegetation green-up. Additionally, bighorn sheep on the Stansbury Mountains (ecologically similar release site) gave birth at similar times as did bighorns on Antelope Island (source area).
Conclusions. Populations of bighorn sheep that were reintroduced into adjacent ecoregions adjusted timing of births to environments and green-up of vegetation in restoration areas. Timing and synchrony of births for reintroduced bighorn sheep in an ecologically similar release site were the same as those of their source area.
Implications. Consideration should be given to the adjustment of timing and synchrony of births when reintroducing bighorns, especially when animals are released into different ecoregions. Also, biologists should select release sites that are ecologically similar to source areas, thereby reducing potential negative effects of animals adjusting timing and synchrony of births to environmental conditions of restoration areas.
Context. Population management of meso-large game species; knowledge of seasonal movements and sexual segregation.
Aims. We predicted (1) a similar mixed spatial tactic in the two sexes (shifters and residents); (2) that reproductive success could be a key factor eliciting a mixed spatial tactic in hinds; and (3) that hunting activities may affect the rutting season, influencing rutting site location.
Methods. We studied the spatial behaviour of 41 red deer on the Italian north-eastern Alps, from December 2003 to October 2007, by VHF radio-tracking.
Key results. For both sexes, two main spatial tactics were described, including residents, remaining in the same area all year long, and shifters, using non-overlapping seasonal home ranges. Most deer showed consistent spatial behaviour. In all, 87% of stags and 49% of hinds were shifters. Sexual segregation was greater in winter than in summer. All hinds wintered in the same valley, with residents in the qualitatively poorer, but protected, area. Resident hinds showed a variable yearly reproductive success, whereas usually all shifters had a calf at heel. Rutting areas of hinds overlapped with their winter or summer ranges, whereas stags occupied up to three different areas yearly. Deer distribution determined a different harvesting pressure on the two sexes.
Conclusions. Although shifters and residents were found in both sexes, differences in spatial behaviour of stags and hinds were consistent for seasonal occupancy, habitat selection and number of seasonal home ranges. For hinds, a mixed spatial tactic, seasonality and hunting activities could be key factors of reproductive success.
Implications. Hunting could affect the proportions of shifter and resident hinds at different levels, with the latter benefiting from the protection accorded. This unequally distributed selective harvesting may alter the local social structure and population dynamics in the long term. Shifter behaviour, seasonal movements and sexual segregation may bias population estimates, if counts are conducted when individuals make seasonal movements. Furthermore, the size of a hunting unit should be function of the extent of local movements of deer.
Context. Increasingly, ornithologists are being asked to identify major sources of avian mortality so as to identify conservation priorities.
Aims. Considerable evidence suggests that windows of office towers are a lethal hazard for migrating birds. The factors influencing the risk of bird–window collisions in residential settings are not understood as well.
Methods. Citizen scientists were requested to participate in an online survey that asked about characteristics concerning their homes and yards, general demographic information about participants, and whether they had observed evidence of bird–window collisions at their home.
Key results. We found that 39.0% of 1458 participants observed a bird–window collision in the previous year. The mean number of reported collisions was 1.7 ± 4.6 per residence per year, with 38% of collisions resulting in a mortality.
Conclusions. Collisions were not random, with the highest collision and mortality rates at rural residences, with bird feeders > rural residences without feeders > urban residences with feeders > urban residences without feeders > apartments. At urban houses, the age of neighbourhood was a significant predictor of collision rates, with newer neighbourhoods reporting fewer collisions than older neighbourhoods. Most people remembered collisions occurring in the summer months.
Implications. Our results are consistent with past research, suggesting that window collisions with residential homes are an important source of mortality for birds. However, we found large variation in the frequency of collisions at different types of residences. Proper stratification of residence type is crucial to getting accurate estimates of bird–window collisions when scaling local data into larger-scale mortality estimates.
Context. For management decisions that require accurate and precise estimates of large mammal population numbers, aerial surveys are considered reliable despite their cost. However, aerial surveys may still suffer from underestimation because of undetected animals and low precision as a result of inefficient sampling designs.
Aims. We assess detection of two species of deer in prairie-parkland communities of western Canada and evaluate a suite of survey design features for improving the accuracy and precision of population estimates from aerial surveys.
Methods. Modelling detection of deer was based on 100 sightability trials involving 54 radio-collared white-tailed and 46 mule deer. We used empirical survey data to simulate surveys under three alternative stratification approaches, schemes for grouping strata, and allocations of survey effort and compared the precision and accuracy of the resulting population estimates.
Key results. We observed deer in 83 of the 100 trials, with detection decreasing with small group size, reduced deer activity, low snow cover, high forest cover and observer fatigue. Survey precision and accuracy were highest when stratification was based on natural breaks, calculated via Jenks optimisation, in the values of resource-selection function (RSF), although improvement was less pronounced for estimates of mule deer abundance. Optimal or equal allocation of sampling effort among strata outperformed proportional allocation of sampling effort. Use of RSF for stratification reduced the coefficient of variation (CV) in estimates of deer numbers from 38% to 23% for white-tailed deer and from 33% to 27% for mule deer compared with past approaches.
Conclusions. Stratification based on RSF values improved precision of deer surveys the most; however, using even simple measures related to habitat selection can improve population estimates. Where deer are highly aggregated, reliably recording all variables needed to implement sightability models can prove problematic; however, survey detection adjustments are nevertheless important to account for the relatively small, but still significant, proportion of missed animals in open prairie–parkland environments.
Implications. Field experiments to assess aerial survey design are impractical because of cost. We illustrate how simulated surveys using empirical data can be useful to evaluate alternative survey designs to improve population estimates in a region when high accuracy or precision are needed to address management questions or to calibrate more cost-effective approaches.
Context. Nearly 20% of black-faced spoonbills (Platalea minor), a globally endangered species, winter along the coasts of the Pearl River Estuary, China. However, these wintering habitats are threatened by urban development. Especially in Macao, road construction for the tourism industry has resulted in habitat deterioration.
Aims. Our study aimed to assess the effects of traffic noise on the distribution and behaviour of black-faced spoonbills in the Taipa–Coloane Wetland Reserve, Macao SAR.
Methods. We built a traffic-noise prediction model for habitat-suitability division. Then we investigated the relationship between traffic noise and diurnal of spoonbill behaviours by collecting traffic-noise data on surrounding roads and observing the activity of black-faced spoonbills in the area over two winters, from 2007 to 2009.
Key results. The maximum number of individuals present in a single month was 50 in the winter of 2007–08 (in February) and 52 in the winter of 2008–09 (in January). Continuous traffic noise was 46.5 and 45.4 dB(A), respectively, at roosting sites in two ecological zones. On the basis of the prediction model, only 10.8 of 30.3 ha were suitable for spoonbills, with noise levels lower than 47 dB(A). Most of the time, the spoonbills were acclimated to the traffic and were not alarmed. However, heavy trucks with a high noise level of 81.8 ± 2.3 dB(A) sometimes disrupted spoonbill behaviour.
Conclusions. The traffic noise around the Taipa–Coloane Wetland Reserve did exist but did not substantially affect black-faced spoonbills. For the birds mainly roosting in a quieter area, the small area of suitable habitat may indirectly limit population growth.
Implications. The fences around Ecological Zone I were successful in minimising visual stimuli from human activities and passing cars. To maintain the suitability of the winter habitat in Macao, restrictions on traffic flow, especially on heavy truck volume, are necessary for spoonbill conservation.
Context. The loss of large predators has been linked with the rise of smaller predators globally, with negative impacts on prey species (mesopredator release). Recent studies suggest that the dingo, Australia’s top terrestrial predator, inhibits predation on native mammals by the invasive red fox, and therefore reduces mammal extinctions. Feral cats also have negative effects on native mammals, but evidence that dingoes suppress cats remains equivocal.
Aims. We sought to examine whether dingoes might spatially or temporally suppress the activity of feral cats at a site containing the sole wild population of an endangered macropod subject to feral cat predation (the bridled nailtail wallaby).
Methods. We used camera traps to compare coarse and fine-scale spatial associations and overlaps in activity times of mammals between August 2009 and August 2010.
Key results. Dingoes and cats used the same areas, but there was evidence of higher segregation of activity times during wet months. Potential prey showed no spatial avoidance of dingoes. Peak activity times of dingoes and their major prey (the black-striped wallaby) were segregated during the wetter time of year (December to March). We did not find evidence that cats were spatially excluded from areas of high prey activity by dingoes, but there was low overlap in activity times between cats and bridled nailtail wallabies.
Conclusions. These findings support the contention that fear of dingoes can sometimes affect the timing of activity of feral cats. However, cats showed little spatial avoidance of dingoes at a coarse scale.
Implications. Control of dingoes should not be abandoned at the site, because the potential moderate benefits of reduced cat activity for this endangered and geographically restricted wallaby may not outweigh the detrimental effects of dingo predation.
Context. European rabbits (Oryctolagus cuniculus) are reaching plague proportions again in some parts of New Zealand as the effect of rabbit haemorrhagic disease begins to wane. Effective monitoring techniques are required to quantify the success of alternative methods of controlling rabbits, such as poisoning.
Aim. To evaluate camera traps as a method of estimating the percentage of rabbits killed in a poison control operation, and to compare results obtained from cameras with those from traditional monitoring methods (spotlight transects and vantage-point counts).
Methods. We deployed cameras and conducted vantage-point counts and spotlight transects to compare a priori statistical power. We then used these monitoring methods to estimate percentage kill from a case study rabbit-control operation using sodium fluoroacetate (compound 1080).
Key results. Cameras had good statistical power to detect large reductions in rabbit numbers (>90%) and the percentage kill estimated using cameras was comparable with spotlight transects and vantage-point counts.
Conclusions. Cameras set up at fixed sampling locations can be an effective method of quantitatively assessing rabbit population control outcomes. We recommend that ≥6 cameras per 100 ha should remain active for at least 5 days before and 5 days following control, so as to obtain reliable estimates of percentage kill.
Implications. Cameras may be preferable to conventional monitoring methods where there is insufficient area to walk or drive transects, terrain is too rugged or scrubby for transects, and there are no or few vantage points from which to count rabbits.
Context. Environmental DNA, or eDNA, methods are a novel application of non-invasive genetic sampling in which DNA from organisms is detected via sampling of water or soil, typically for the purposes of determining the presence or absence of an organism. eDNA methods have the potential to revolutionise the study of rare or endangered taxa.
Aims. We evaluated the efficacy of eDNA sampling to detect populations of an amphibian of conservation concern, the eastern hellbender (Cryptobranchus a. alleganiensis), indirectly from their aquatic environments.
Methods. We developed species-specific primers, validated their specificity and sensitivity, and assessed the utility of our methods in silico and in laboratory trials. In the field, we collected water samples from three sites with known densities of hellbenders, and from one site where hellbenders do not occur. We filtered water samples, extracted DNA from filters, and assayed the extraction products for hellbender DNA by using polymerase chain reaction (PCR) and gel electrophoresis.
Key results. Our methods detected hellbenders at densities approaching the lowest of reported natural densities. The low-density site (0.16 hellbenders per 100 m2) yielded two positive amplifications, the medium-density site (0.38 hellbenders per 100 m2) yielded eight positive amplifications, and the high-density site (0.88 hellbenders per 100 m2) yielded 10 positive amplifications. The apparent relationship between density and detection was obfuscated when river discharge was considered. There was no amplification in any negative control.
Conclusion. eDNA methods may represent a cost-effective means by which to establish broad-scale patterns of occupancy for hellbenders.
Implications. eDNA can be considered a valuable tool for detecting many species that are otherwise difficult to study.
Context. According to the tens rule, 10% of introduced species establish themselves.
Aims. We tested this component of the tens rule for amphibians and reptiles globally, in Europe and North America, where data are presumably of good quality, and on islands versus continents. We also tested whether there was a taxonomic difference in establishment success between amphibians and reptiles.
Methods. We examined data comprising 206 successful and 165 failed introduction records for 161 species of amphibians to 55 locations, and 560 successful and 641 failed introduction records for 469 species of reptiles to 116 locations around the world.
Key results. Globally, establishment success was not different between amphibians (67%) and reptiles (62%). Both means were well above the 10% value predicted by the tens rule. In Europe and North America, establishment success was lower, although still higher than 10%. For reptiles, establishment success was higher on islands than on continents. Our results question the tens rule and do not show taxonomic differences in establishment success.
Implications. Similar to studies on other taxa (birds and mammals), we found that establishment success was generally above 40%. This suggests that we should focus management on reducing the number of herptile species introduced because both reptiles and amphibians have a high likelihood of establishing. As data collection on invasions continue, testing establishment success in light of other factors, including propagule pressure, climate matching and taxonomic classifications, may provide additional insight into which species are most likely to establish in particular areas.
Context. Lands without agricultural or urban use embedded within agricultural and urban regions now account for ∼35% of Earth’s terrestrial extent. Although created by human disturbances, these ‘novel ecosystems’, usually poor in native flora and often dominated by alien species, do not require human intervention for their maintenance. Given their large and increasing area, however, their ability to support native – and especially threatened – faunas warrants investigation. With 20 species already extinct and 47 of its 91 extant species assessed as Endangered or Critically Endangered, Sri Lanka’s amphibian fauna is in trouble. The 18 anurans (12 of these Endangered) occurring above 1500 m in the island’s central mountains are at particular risk from drastic declines in the extent and quality of habitat. Habitat restoration, however, is retarded by successional vegetation being arrested at least in the decadal time-frame by alien invasive species, creating a ‘novel ecosystem’.
Aim. To investigate whether such an ecosystem is able to support native anurans with a species richness and abundance comparable to that of neighbouring tropical montane cloud forest.
Methods. We surveyed 110 transects (each 20 m × 2 m) across three neighbouring locations covering three microhabitat-types, and recorded 552 specimens. One-way analyses of variance and post hoc, pair-wise Tukey’s tests were performed to test for differences in species richness and abundance among the three microhabitat types.
Key result. Of the 15 anuran species occurring in the neighbouring primary forest, 12 (eight of them Endangered) had established populations in the novel ecosystem (a former tea plantation), with abundances comparable to (or in some cases exceeding) those in primary forest.
Conclusion. Even young secondary forest dominated by alien plant species, in which native vegetation is almost wholly absent, can provide adequate habitat for most threatened highland anurans in Sri Lanka.
Implications. (1) Even if florally poor and dominated by alien species, novel ecosystems may present potential conservation opportunities for previously threatened faunas. (2) Threatened anurans exclusively dependent on primary forest and unable to utilise secondary-growth forest should receive greater conservation attention and be prioritised for in situ conservation measures. (3) Given their large and increasing extent globally, novel ecosystems should be considered as part of the area of occupancy of species able to complete their life cycles in them when assessed for conservation purposes, rather than being arbitrarily discarded as ‘degraded’.
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