Biology subjects

Spong, G.

Publications and source records attributed to Spong, G..

4 recordsLinked to original sources

bioRxiv2026

Mortality causes and annual survival rates of red foxes (Vulpes vulpes).

Mortality causes and survival rate estimates from individual follow-ups of GPS-collared animals provide reliable demographic data, but such estimates are rare for red foxes Vulpes vulpes. We used data from 126 GPS-collared red foxes tracked between 2011 and 2019 across a latitudinal gradient in central Sweden and Norway to quantify mortality causes and estimate annual survival probabilities using the Andersen-Gill extension of the Cox proportional hazards model. Hunting was the dominant mortality cause (63%), followed by vehicle collisions (14%), stress or malnutrition (11%), sarcoptic mange (9%), and predation (3%). Annual survival was 0.58 for adults and 0.32 for subadults. Subadults had approximately twice the hazard of adults, males had elevated hazard relative to females, and mortality risk was highest in autumn and early winter. These collar-based estimates are strikingly similar to mark-recovery estimates from the same region nearly five decades earlier, despite an intervening population collapse from sarcoptic mange, subsequent full recovery, and a major decline in harvest pressure. This convergence is consistent with density-dependent regulation at a food-determined and food-limited carrying capacity, suggesting that current harvest levels are not limiting the population. Furthermore, human-caused mortality was approximately four times greater than natural mortality, illustrating that living in close proximity to humans -- which often favours generalist predators such as red foxes -- may also come at a cost of increased mortality risk. Developing validated census methods for red foxes in boreal Scandinavia is identified as a key priority for quantitative population management.

ecology↗

bioRxiv2026

Latitudinal effects on weight and age-dependent survival of red fox Vulpes vulpes

Age-dependent survival is central to understanding population dynamics and life-history evolution. We analysed carcass weight and age-at-harvest data from 6 022 red foxes (Vulpes vulpes) collected across Sweden between 1967 and 1971 to evaluate latitudinal effects on body mass and age-dependent survival. Carcass weights decreased from south to north in both adults and sub-adults, contrary to Bergmanns rule, with southern foxes weighing approximately 1.27 times more than northern foxes. The latitudinal weight gradient exceeded the sex difference in both age classes, and no sex x region interaction was detected. The decrease in weight with latitude is consistent with reduced prey availability and harsher winter conditions in the north, which limit growth and body size during development. Using a Bayesian age-at-harvest model with region-specific population growth rates ({lambda}), we estimated age-dependent survival probabilities for four latitudinal regions and both sexes. Despite the strong latitudinal gradient in weight, survival did not show a corresponding pattern -- regional differences were uncertain, with all credible intervals spanning zero. Regional population growth rates were consistent with slight decline in the north and near-stability in the south-central region, which suggests that body condition and population dynamics are coupled at the regional scale despite no survival gradient. The decoupling of body condition and survival across regions suggests that mortality patterns are similar across the latitudinal gradient. We discuss these patterns in terms of latitudinal productivity gradients, prey availability, and life-history trade-offs in a widely distributed carnivore.

ecology↗

bioRxiv2024

SNP panel for non-invasive genotyping of leopard (Panthera pardus)

Genetic resources for species monitoring should ideally be relevant for the species full distribution range, feasible economically and logistically, and validated for the range of sample types collected from the field. This is particularly important for large carnivores that are elusive and wide-ranging, where individual and population processes often traverse administrative borders, and where obtaining high-quality samples can be challenging. Here we present a small species-specific SNP panel for leopards. We used whole genome data from across the global range and RAD sequence data from Zambian leopards to select markers for assay development. These were ascertained for 590 individual leopards from eight African countries and final selection was based on marker variation and performance on non-invasive samples. The final 96 marker panel holds 5 mitochondrial markers for species recognition, 3 Y-markers for determination of individual sex, 3 X-markers and 85 somatic markers, with an associated genetic baseline holding nearly 900 individuals. The selected autosomal markers hold variation across the global range with high power to identify individuals (PID=2,45x10-35) and in most cases their provenance with high assignment probability (>95%). Markers were also selected based on their performance on samples with low target DNA content, with distinct genotype separation in the output marker plots. The genotypes from this panel are thus straightforward to analyze and do not require computationally challenging bioinformatic resources, making this a low cost and accessible resource for leopard monitoring and research.

genetics↗

bioRxiv2024

Linear infrastructure and associated wildlife accidents create an ecological trap for an apex predator and scavenger

Animals can be caught in an "ecological trap" when they select for seemingly attractive habitats at the expense of their fitness. Such maladaptive behaviour is often a consequence of human induced rapid changes in animals natal environment such as building of energy and transportation infrastructure. We tested the ecological trap hypotheses for human created linear infrastructure on a widely distributed apex predator and a scavenger - the Golden eagle (Aquila chrysaetos), whose range spans across the entire northern hemisphere. Roads and railways create novel and attractive feeding subsidies through traffic induced mortality of other species, while powerline areas provide perching or nesting sites and scavenging opportunities from electrocuted or collision-killed birds. These conditions lead to negative demographic consequences for eagles. We used integrated step selection functions for habitat selection and movement behaviour with ten years of data from 74 GPS-tracked Golden Eagles (36 adult and 38 immature) in Fennoscandia. To measure habitat attractiveness, we use wildlife traffic accident statistics on major wildlife species including the eagles, and mortality of five GPS- tracked eagles to show demographic consequences. Eagles selected for linear features all year round and across entire study region. Individuals also searched and sat alongside roads and railway lines more frequently. Immature eagles selected roads and railway sites more consistently compared to adults and showed learning behaviour with age. We discuss implications of these findings for conservation and population ecology of apex predators and scavengers and their potential evolutionary implications. We suggest that rapid removal of carcasses from roads and tracks is urgently needed to avoid this trap for many raptor and scavenger species throughout the world and develop methods and approaches to reduce wildlife traffic accidents all together.

ecology↗