Simple Habitat Research Articles

Terrestrial vertebrate fauna in a multifunctional landscape in Gabaldon, Nueva Ecija, Philippines

Abstract. Gojo-Cruz PHP, Caldito JC, Catubig YDL, Cornes HM, Corpuz JS, Maniquiz SS, Matunan KGE, Pascual FJ, Miguel ESS, Siguancia GC, Turqueza DC, Madlao JP, Cruz CF, Merculio JG. 2024. Terrestrial vertebrate fauna in a multifunctional landscape in Gabaldon, Nueva Ecija, Philippines. Biodiversitas 25: 583-597. This study was done to document the vertebrate fauna in a multifunctional landscape at the foothills of Mt. Mingan, Gabaldon, Nueva Ecija. The inventory of wild vertebrate fauna associated with the different habitat types in the area will be valuable in creating suitable management programs to reduce the impact of human activities in the area without affecting local economic activities. Standard survey techniques, including day and night transect walks, opportunistic surveys, mist-netting, and cage trapping, were employed to document vertebrate fauna in the agro-forest, around built-up areas, forest edges, lowland forest, grassland, and riparian habitats. A total of 79 species of vertebrate fauna were recorded, including 7 species of mammals, 13 species of reptiles, 9 species of amphibians, and 50 species of birds. Thirty-three (33) species were endemic to the Philippines. Regarding conservation status, eight (8) species were listed in the higher threat status under DAO 2019-09. Species richness was observed to be highest in lowland dipterocarp forests. On the other hand, species composition varies between habitats, with endemic species being more common in complex habitats such as lowland dipterocarp forests than in simpler habitats like agricultural areas. The high species richness and the presence of endemic and threatened species in the multifunctional landscape of the area highlight the need for management plans considering habitat heterogeneity and connectivity.

Ice type matters: impacts of landfast and drift ice on body condition in a high Arctic seabird community

Sea ice, a central component of polar ecosystems, is undergoing profound changes due to climate change. In particular, the Arctic is experiencing unprecedented warming at quicker rates than other regions. This alarming trend of sea ice loss has dire consequences, with spill-over effects on the entire ecosystem, from phytoplankton to top predators. The complex and dynamic nature of sea ice gives rise to diverse habitats, each with the potential to affect larger ecosystems in different ways. However, our understanding of the relative importance of different ice types for higher trophic levels remains limited. To address this knowledge gap, we conducted a comprehensive study of the effects of drift ice, landfast ice, and total sea ice extent (landfast ice + drift ice) on the body condition of six species of polar-breeding seabirds using long-term monitoring data (2003-2021) from Kongsfjorden, Svalbard. These species fell into two categories: Arctic species (Little Auk Alle alle, Brünnich’s Guillemot Uria lomvia, and Glaucous Gull Larus hyperboreus) and “boreal” (or north temperate) species (Black-legged Kittiwake Rissa tridactyla, Arctic Skua Stercorarius parasiticus, and Great Skua Stercorarius skua). We found that the presence and extent of different types of sea ice may have different effects on seabird body condition. Though we did not find any relationship between total sea-ice extent and seabird body condition, drift ice and landfast ice extent did produce significant effects. For Arctic species, these effects were positive. For boreal species, the relationship between body condition and drift and landfast ice was more complex. Our study suggests that the use of a non-specific sea ice variable may mask the effects of sea ice on Arctic wildlife, highlighting the importance of not considering sea ice to be uniform and simple habitat.

Effects of turbidity and habitat complexity on the foraging behavior of the black bullhead (Ameiurus melas)

ABSTRACT The role of vertebrate scavengers in nutrient flow of aquatic ecosystems has recently been emphasized. Evidence is accumulating that scavenging is an alternative tactic for certain predatory fish, but their foraging choices between scavenging and predation under varying environmental conditions have not been studied. In this study, we presented black bullheads, Ameiurus melas (Rafinesque, 1820), with both live and carcass prey of tubenose gobies, Proterorhinus semilunaris (Heckel, 1837), in aquaria with varying levels of turbidity and habitat complexity. Our findings revealed that black bullheads exhibit higher consumption of carcass prey in complex habitat and clear water conditions. We also provide evidence of the active predatory behavior displayed by black bullheads; a greater consumption of live prey was observed in simple habitat and turbid water. We found no relationship between individual exploratory behavior and the choice between carcass and live prey in black bullheads. Our results suggest that the choice between scavenging versus predatory foraging strategy under varying environmental conditions is influenced by the behavior of both consumer and prey. The ability of black bullheads to adapt their foraging strategy in different environments may contribute to their widespread success as an invasive species.

Diel activity patterns and habitat preferences of stonefish (Synanceia spp.) in captivity

Synanceia verrucosa (reef stonefish) and Synanceia horrida (estuarine stonefish) are known as the world’s most venomous fishes. However, little is known about their habitat preference and activity patterns. This study aimed to determine the habitat preferences and diel activity patterns of stonefish. The movements of four adults of each species that were offered complex and simple habitats in captivity were recorded by filming during day and night periods. Generally, both species exhibited similar behaviour, though S. verrucosa travelled further per movement than S. horrida. Collectively, stonefish spent 94% of their time associated with complex habitat and moved significantly less frequently on complex (1.6 movements per hour) relative to simple habitat (17.3 movements per hour). Stonefish were least active around sunset in the late afternoon and evening, which may relate to an active feeding period during the morning or paradoxically to a higher probability of ambush feeding success near sunset. These findings have enhanced our current understanding of the ecology of these species.

Manatees in Zoological Parks throughout the World: History, State, and Welfare.

The order Sirenia comprises several species of manatees and one species of dugong. These popular marine mammals are relatively recent acquisitions to zoological parks throughout the world. As far as we know, there are less than 200 manatees, mostly American, a few African, and ever less Amazonian, currently in zoological parks. American manatees are predominantly found in zoos in Europe, North America, and in some Asian countries, while African ones are present exclusively in Asian zoos. The living conditions of captive manatees differ considerably from zoo to zoo (i.e., numbers, sex ratio, outdoor vs. indoor habitats, complex vs. simple habitats). Most research on manatee behaviour has been relatively recent, and studies on cognition, sociality, and ecology have a significant impact on our perception of manatee needs and management, with wider implications for their welfare. In the wild, manatees demonstrated various cognitive capacities; spatial memory and learning abilities play an important role in their daily life in a complex and dynamic environment. Furthermore, there is evidence that these mammals are more social animals than expected. Individuals show various personality traits on the boldness-shyness continuum and their sociality varies. All those parameters are important in terms of animal welfare. Several behavioural studies showed that standardized enrichment programs benefit and ensure the welfare of captive zoo animals. However, obtaining accurate information on the presence of manatees in zoos, living conditions, management, and consequently welfare remains challenging. This study examines the current knowledge on manatee behaviour and cognition and then discusses different approaches to improving the welfare of this charismatic marine mammal in zoological parks.

Each Personality Performs Its Own Function: Boldness and Exploration Lead to Differences in the Territoriality of Swimming Crabs (Portunus trituberculatus).

The boldness and exploration of animals are closely related to their territoriality, with relevant studies having important applications in wildlife conservation. The present study establishes a behavior observation system measuring the boldness and exploration of swimming crabs (Portunus trituberculatus) to clarify the relationship between boldness, exploration, and territoriality, as well as to provide a behavioral basis for the construction of marine ranching. The behavioral tests of crabs in a safe environment (predator absence), a dangerous environment (predator presence), and habitat selection (complex and simple habitat) are analyzed. A territorial behavior score is calculated as an evaluation index of territoriality. The correlation between the swimming crabs' boldness, exploration, and territoriality is analyzed. The results show that there is no boldness-exploratory behavioral syndrome. In predator absence or presence environments, boldness is dominant in territorial behavior and positively correlates with territoriality. Exploration plays a vital role in habitat selection tests but has no significant correlation with territoriality. The experimental results preliminarily show that boldness and exploration jointly develop the difference in the space utilization ability of crabs with different personalities, improving the adaptability of swimming crabs in different conditions. The results of this study supplement the behavior rules of the dominant species of typical fishery resources in marine ranches, providing a basis for achieving animal behavior management function in marine ranches.

Detecting the impact of the “Grain for Green” program on land use/land cover and hydrological regimes in a watershed of the Chinese Loess Plateau over the next 30 years

To increase vegetation coverage and improve ecosystem services, the government has promulgated and implemented the “Grain for Green” policy since 1999. How and where vegetation cover increases and how land use/land cover (LULC) changes determine regional water resources and hydrological regimes. On the Chinese Loess Plateau (LP), an arid and semiarid area with fragmented topography and the transitional vegetation nature, accurately predicting LULC and vegetation change is particularly important. We employed a simple habitat analogy approach, and the Soil and Water Assessment Tool (SWAT) to predict potential vegetation restoration and LULC change and investigated their impact on the hydrological regime in a watershed of Liujiahe. Results showed that the maximum recoverable vegetation cover of the Liujiahe watershed is 71.1%, of which 9.2% still has potential for vegetation cover and 36.4% of the area vegetation continued to improve in the future. Future suitable afforestation areas are limited to 46.06 km2, which will result in cropland will decrease by 47.4%, and grassland and forestland will increase by 15.8% and 0.7%, respectively. However, SWAT results showed that vegetation restoration between the 1980 s and 2020 s has already reduced the annual mean runoff and soil water content (SW) by 44.2% and 43.9%, respectively, while evapotranspiration (ET) has increased by 12.6%; LULC changes in the next 30 years will further reduce runoff and SW by 15.6% and 11.1% respectively, and increase ET by 1.2%. Overall, large-scale vegetation restoration has greatly affected hydrological regimes on the LP. The area still has potential for vegetation enhancement; however, considering the limited rainfall and water-carrying capacity, the vegetation restoration of this watershed should be based on natural restoration or low water consumption grasses and shrubs to avoid a water resource crisis. These results provide a perspective for modelling LULC changes in areas with fragmented terrain and highly influenced by human activities, and provide an important basis for sustainably managing natural resources on the LP under long-term ecological restoration.

A comparison of methods for estimating juvenile salmon habitat capacity to assist with restoration planning and evaluation

AbstractObjectiveA variety of analytical approaches have been developed in recent years to estimate salmon Oncorhynchus spp. freshwater habitat capacity to assist with planning and evaluating habitat restoration. We compared and contrasted seven different methods for estimating juvenile Chinook Salmon O. tshawytscha habitat rearing capacity (total number of fish that a given area of habitat can support), abundance, and habitat suitability in a 3.2‐km reach of the Grande Ronde River, Oregon.MethodsThis included approaches that used statistical methodologies applied to existing empirical data sets, including quantile random forests (QRFs) and spatial stream networks (i.e., Fish Data Analysis Tool [FDAT]), and deterministic models that included the habitat suitability index, the unit characteristic method (UCM), and three habitat expansion methods.ResultWe hypothesized that the methods would provide comparable estimates. However, the approaches provided very divergent estimates for the same stream reach, ranging from 1048 to 24,530 juvenile Chinook Salmon. The simple habitat expansion methods appeared to be the most similar to the actual parr (juvenile) abundance obtained from recent snorkel surveys (4179 juveniles). The fish density data (fish/m2) and habitat data used in the models were likely the main drivers of the differences between the UCM and habitat expansion methods.ConclusionThe habitat expansion approaches, which are based on detailed habitat surveys, appear to be particularly suitable for estimating capacity within a reach; thus, they may be suitable for evaluating changes due to habitat restoration. The model‐based approaches (QRF and FDAT) appear to yield coarser estimates, in part because they use various inputs at the reach and landscape scales. As such, they are more useful for relative comparisons among reaches in watersheds to assist with watershed‐scale restoration planning and prioritization. Because all of the methods rely on fish density in different types of habitats, regional or local data on fish densities would improve their accuracy.

Molecular population genetic analysis of Eriocheir japonica inhabiting Andeok Valley

Eriocheir japonica inhabit rivers flowing into the East Sea, South Sea, and the coastal waters of Jeju-do in South Korea, Japan, and Sakhalin. The larvae migrate to freshwater, mature, and move to estuaries to spawn. Jeju-do has habitats that prevent the migration of aquatic organisms. Populations with low within-group genetic diversity experience increased extinction risk. Industrialization causes climate change and also creates species extinctions. The goal of this study was to investigate the genetic diversity of E. japonica inhabiting Andeok Valley to elucidate their genetic stability and encourage future conservation plans. E. japonica samples used for the study were from the Andeok Valley in South Korea. One walking leg was used for DNA extraction. DNA was amplified using polymerase chain reaction to sequence mitochondrial cytochrome c oxidase subunit 1 (CO1) and cytochrome b (CytB) genes. Haplotype and sequence diversity analyses were performed. Sequencing results for CO1 and CytB genes, included 658 and 651 base pairs, respectively. The median network analysis showed that the population inhabiting Andeok Valley had a genetically simple phylogenetic structure. This region provides simple habitat conditions, preventing gene transfer. The probability of extinction of E. japonica that inhabits Andeok Valley is markedly high.

The link between animal personality and habitat selection in males of the Neotropical poison frog Allobates femoralis.

Environmental variation plays a key role in the evolution and maintenance of animal personality. Individuals with different personality types might exhibit different habitat preferences. Alternatively, variation in individual behaviour across space could arise as a plastic adaptation to distinct habitats. Our study aims to investigate if habitat choice is influenced by an individual's personality. We assessed individual levels of activity, boldness, and exploration in male poison frogs, and performed a habitat choice test under controlled laboratory conditions. Individuals were consistent in their behaviours, but all tested frogs chose the complex over the simple habitat. Individuals that were characterized as bold and very explorative also showed more movements between the two different habitats in the choice test. These results indicate that personality measured in a highly standardized artificial setup, such as a novel environment test, indeed can reflect boldness and exploration related behaviours measured in a more naturalistic setup.

Effect of habitat topography on the structure and diversity of benthic communities across five marinas from the southwestern Atlantic Ocean

AbstractMarine urbanization promotes the addition of hard substrata that barely resembles natural substrate nearby. We manipulated habitat topography in five marinas across one of the most populated regions from the Southwestern Atlantic Ocean to describe the effect of habitat complexity on the diversity of benthic communities across sites with distinct conditions and biotas. The highest biomass was found in the two marinas under high pollution and freshwater disturbances, regardless of habitat complexity. Habitat topography did not affect species richness but determined the structure of sessile communities in all marinas. The structure of mobile communities was affected only in the most diverse site, increasing the abundance of isopods. In general, fragile ascidians, hydrozoans, and non‐calcified polychaetes dominated complex habitats, while structurally defended animals such as barnacles, serpulids, and encrusting bryozoans dominated simple habitats, suggesting that dominant species are selected by habitat complexity based on their morphological traits. However, the final community structure was also determined by differences across marinas, suggesting that the effect of increasing habitat topography is mostly site‐specific. Therefore, strategies to minimize the disparity between natural and artificial habitats must consider historic local community and a multiple stressors scenario.

Exploration and spatial cognition show long-term repeatability but no heritability in the Aegean wall lizard

Recently, biologists have become increasingly interested in cognitive variation among individuals and how it relates to differences in fitness. However, very few studies so far have studied the long-term repeatability and heritability of cognitive performance in wild animals. This is nevertheless crucial information to fully understand the potential ecological and evolutionary impact of individual variation in cognitive performance. In 2019, we assessed exploration, problem solving and spatial and reversal learning in 66 Aegean wall lizards, Podarcis erhardii , then released them in seminatural enclosures consisting of either simple or complex habitat. One year later, we recaptured and retested the surviving lizards and their offspring to estimate the long-term repeatability and heritability of these behavioural and cognitive characteristics. We found that exploration and spatial learning were moderately repeatable, but reversal learning only marginally and learning flexibility and problem solving not at all. Reversal learning ability declined over time in lizards kept in simple habitat, but not in those kept in complex habitats – suggesting habitat-dependent cognitive plasticity. To our knowledge, this is the first study demonstrating (long-term) consistency in cognitive traits within a nonavian reptile. The combination of modest repeatability and low heritability does suggest that, within our study species, personality and cognitive variation among individuals and populations is mostly moulded by environmental effects. • We tested repeatability and heritability of exploration and cognition in lizards. • Only exploration and spatial learning were moderately repeatable between years. • Reversal learning was marginally repeatable. • Lizards showed habitat-dependent changes in their reversal learning abilities. • Heritability estimates were low and nonsignificant.

Habitat complexity mediates spatiotemporal niche partitioning among native and invasive seed predators

Red imported fire ants dominate certain food webs in North America due to their omnivorous and aggressive feeding behavior. Structural habitat complexity can mediate effects of invasive predators on native insects, by either facilitating or tempering antagonistic interactions, with potential consequences at lower trophic levels. Along a gradient of habitat complexity, we evaluated how refuge affects the activity and foraging behavior of fire ants and native invertebrate seed predators using video surveillance, and then determined their consumption of pigweed seeds in seed removal assays. Fire ants dominated seed predation in our system, and structural complexity increased both their activity and seed removal, while reducing that of native seed predators. In structurally simple habitats with high sun exposure, fire ant activity was restricted to the evening when temperatures were milder, while native seed predators foraged during the heat of the day, possibly to avoid antagonistic interactions with fire ants. In relatively shaded, structurally complex habitat, the active foraging period for fire ants expanded earlier into the heat of the day, and almost totally overlapped with that of native seed predators. Our data suggest that structural refuge may facilitate antagonism and site/resource domination by fire ants.

Sex, size and habitat complexity effects on emergence latency and latency to locate food of the invasive porthole livebearer (Poeciliopsis gracilis).

Biological invasions are considered the second major cause of plant, amphibian, reptile, and mammal loss worldwide. Like islands, freshwater ecosystems are especially susceptible to the negative impacts of invasions. The porthole livebearer (Poeciliopsis gracilis), recently identified as invasive in the Mexican Central Plateau, is increasing its populations and could impact freshwater ecosystems like its cousin species the guppy (Poecilia reticulata). Risk-taking behaviours, such as emergence latency, are recognised as key characteristics to invasion success and Poeciliid females can establish a viable population by themselves (due to their multiple paternity broods). We investigated the emergence latency and latency to locate food in simple and complex environments of porthole livebearers, including the effect of their size and sex. For both sexes, bigger fish emerge less times and take longer to do so, but females are faster to exit the refuge than males. We found no differences in porthole livebearer’s behaviour in complex or simple habitats, and no significant differences between sex, size or treatment in the time to locate food after exiting the refuge. Our results suggest that the benefit of faster emergence from the refuge in porthole livebearers in novel environments could be higher for females. We consider that porthole livebearer females being bolder could contribute to the invasion success of the species. Our study points at females and smaller fish as being the more likely to explore novel environments, which could contribute to understanding how the invasions by the porthole livebearer are driven.

Where and why are species' range shifts hampered by unsuitable landscapes?

There is widespread concern that species will fail to track climate change if habitat is too scarce or insufficiently connected. Targeted restoration has been advocated to help species adapt, and a “conductance” metric has been proposed, based on simulation studies, to predict effective habitat configurations. However, until now there is very little empirical evidence on how the configuration of habitat is affecting expansion at species' cool range margins. We analysed the colonisation events that have occurred in continuously monitored trap locations for 54 species of southerly distributed moths in Britain between 1985 and 2011. We tested whether the time until colonisation was affected by attributes of each species, and of intervening landcover and climate between the trap and the baseline distribution (1965–1985). For woodland species, the time until colonisation of new locations was predicted by the “conductance” of woodland habitat, and this relationship was general, regardless of species' exact dispersal distances and habitat needs. This shows that contemporary range shifts are being influenced by habitat configuration as well as simple habitat extent. For species associated with farmland or suburban habitats, colonisation was significantly slower through landscapes with a high variance in elevation and/or temperature. Therefore, it is not safe to assume that such relatively tolerant species face no geographical barriers to range expansion. We thus elucidate how species' attributes interact with landscape characteristics to create highly heterogeneous patterns of shifting at cool range margins. Conductance, and other predictors of range shifts, can provide a foundation for developing coherent conservation strategies to manage range shifts for entire communities.

Environmental Flows to Estuaries and Coastal Lagoons Shape the Salinity Gradient and Generate Suitable Fish Habitat: Predictions From the Coorong, Australia

Freshwater flows to estuaries shape habitat, transport nutrients to drive productivity, and generate a salinity gradient that impacts water quality and provides spawning cues for fish. The aim of this study was to quantify how environmental flows improved outcomes for a coastal lagoon system (the Coorong, South Australia), considering the export, and prevention of ingress, of salt from the system, and the increased available habitat for key fish biota. A hydrodynamic model was used to simulate salinity and water temperature, and to determine the salt exchange between the Coorong and ocean for the observed conditions with environmental water release included. Scenario simulations showed that maintaining river flow is shown to arrest salt intrusion from the ocean into the Coorong. Without environmental water, the net import of salt into the Coorong would have been considerably greater, ranging between 1.86 million tonnes in 2018–19 to approximately 2.33 million tonnes in 2019–20. The fresher conditions created by environmental water provision supported a considerable expansion of suitable fish habitat area, derived from a simple habitat index based on salinity and water temperature. Without environmental water the habitat suitable for mulloway would have contracted by 38% over the 3 year investigation period. A similar trend is evident for black bream, Tamar goby, greenback flounder, yelloweye mullet, congolli and smallmouth hardyhead. The results highlighted the importance of cumulative benefits from delivering environmental water over multiple years, with different results obtained if the environmental water provided regularly or just focused over a single year. The approach used in this work to relate hydrological changes from water management to indicators of habitat suitability through changes to physical attributes provides information to inform the evaluation of environmental watering, as well as a tool to support future decision making to maximise the benefits from this precious resource.

Influence of habitat complexity on the prey mortality in IGP system involving insect predators (Heteroptera) and prey (Diptera): Implications in biological control.

Intraguild predation (IGP) is common in the freshwater insect communities, involving a top predator, intraguild prey (IG prey) and a shared prey. Influence of the habitat complexity on the prey-predator interactions is well established through several studies. In the present instance, the IGP involving the heteropteran predators and the dipteran prey were assessed in the background of the habitat complexity. The three predators Diplonychus rusticus, Ranatra filiformis, and Laccotrephes griseus, one intraguild prey Anisops bouvieri and two dipteran prey Culex quinquefasciatus and Chironomus sp. were used in different relative density against the complex habitat conditions to deduce the impact on the mortality on the prey. In comparison to the open conditions, the presence of the macrophytes and pebbles reduced the mortality of the shared prey under intraguild system as well as single predator system. The mortality of the shared prey was however dependent on the density of the predator and prey. Considering the shared prey mortality, predation on mosquito larvae was always higher in single predator system than chironomid larvae irrespective of identity and density of predators. However, for both the shared prey, complexity of habitat reduced the prey vulnerability in comparison to the simple habitat condition. Higher observed prey consumption depicts the higher risk to predation of shared prey, though the values varied with habitat conditions. Mortality of IG prey (A. bouvieri) in IGP system followed the opposite trend of the shared prey. The lower mortality in simple habitat and higher mortality in complex habitat conditions was observed for the IG prey, irrespective of shared prey and predator density. In IGP system, the shared prey mortality was influenced by the habitat conditions, with more complex habitat reducing the vulnerability of the shared prey and increased mortality of the IG prey. This implies that the regulation of the mosquitoes, in the IGP system will be impeded by the habitat conditions, with the heteropteran predators as the top predator.

Stock-recruitment models from the viewpoint of density-dependent survival and the onset of strong density-dependence when a carrying capacity limit is reached

When viewed on a discrete time step (e.g., one year) rather than instantaneously, the Ricker and Beverton-Holt stock recruitment relationships describe a strong influence of changes in adult abundance on juvenile survival even at low biomass levels. In fact, they describe a stronger influence at lower adult abundance than at high adult abundance. This is not consistent with a simplistic interpretation of carrying capacity, where survival reduces more rapidly as the juvenile abundance approaches its carrying capacity due to resource limitation. It implies that other processes (e.g., changes in predation risk with increased abundance as described by arena theory) control density dependence. A simple habitat limitation model suggests that a similar relationship can occur if the number of juveniles produced by the adults is always more than the juvenile carrying capacity. However, the resulting stock-recruitment relationship is constant recruitment, while that of the Beverton-Holt is increasing asymptotically and the Ricker is dome shaped. Fluctuations around an average recruitment level for a wide range of adult abundance levels is common for highly fecund pelagic spawners (e.g., tuna), suggesting that the survival and recruitment relationships implied by the simple habitat limitation model might be appropriate for these species. Underpinning this argument is the concept that the adult population will saturate the juvenile carrying capacity unless the adult population is fished to extremely low levels. However, it is reasonable to expect that survival should be density independent, or possibly even decompensatory, at some low level of adult abundance. Ignoring depensation, the survival relationship would therefore be well described by a general logistic equation where the decline in survival initially accelerates as abundance increases and then deaccelerates. The resulting stock-recruitment relationship would be a hockey stick shape with the possibility of reduced recruitment at large stock sizes. The model could also be used for low fecund species (e.g., sharks) for which the juvenile carrying capacity is not saturated until the adult abundance is large (i.e., survival is density-independent for a wide range of adult population sizes). In our model, particularly for high fecund species, temporal variation in recruitment would be controlled by changes in the juvenile carrying capacity. We provide equations for the generalized logistic survival stock-recruitment model and investigate the yield consequences. We suggest that an important management consideration is the level of adult abundance at which the juvenile carrying capacity becomes saturated (i.e., when does density dependence become influential on juvenile survival).

Reliability of environmental DNA surveys to detect pond occupancy by newts at a national scale

The distribution assessment and monitoring of species is key to reliable environmental impact assessments and conservation interventions. Considerable effort is directed towards survey and monitoring of great crested newts (Triturus cristatus) in England. Surveys are increasingly undertaken using indirect methodologies, such as environmental DNA (eDNA). We used a large data set to estimate national pond occupancy rate, as well as false negative and false positive error rates, for commercial eDNA protocols. Additionally, we explored a range of habitat, landscape and climatic variables as predictors of pond occupancy. In England, 20% of ponds were estimated to be occupied by great crested newts. Pond sample collection error rates were estimated as 5.2% false negative and 1.5% false positive. Laboratory error indicated a negligible false negative rate when 12 qPCR replicates were used. Laboratory false positive error was estimated at 2% per qPCR replicate and is therefore exaggerated by high levels of laboratory replication. Including simple habitat suitability variables into the model revealed the importance of fish, plants and shading as predictors of newt presence. However, variables traditionally considered as important for newt presence may need more precise and consistent measurement if they are to be employed as reliable predictors in modelling exercises.

Non-preferred habitat increases the activity area of the endangered northern quoll (Dasyurus hallucatus) in a semi-arid landscape

Animal conservation requires a sound understanding of movement ecology and habitat selection. A key component of this is identifying habitats that animals actively seek or avoid. We quantified habitat selection and investigated the drivers of variability in the short-term activity area of a small, endangered mesopredator, the northern quoll (Dasyurus hallucatus), in the Pilbara region of Western Australia. We collated, standardised, and analysed 14 northern quoll GPS tracking events from four studies conducted between 2014 and 2018. Northern quolls selected activity areas in locations that were more topographically rugged than the broader landscape, characterised by a higher percentage cover of rocky habitat and riverbed, and a lower percentage cover of spinifex sandplain. The size of their activity area also increased with higher percentage cover of non-preferred spinifex sandplain. Therefore, the destruction of habitats preferred by northern quolls – such as mining of rocky habitat – and introduction of structurally simple habitat like spinifex sandplain, is likely to negatively impact resource availability and lead to altered movement patterns that could decrease survival. Future conservation planning should place emphasis on the protection of rugged rocky habitat for northern quolls, as well as efficient movement pathways between patches of this critical habitat.