Factors affecting the crop damage by wild boar (Sus scrofa) and effects of population control in the Ticino and Lake Maggiore Park (North-western Italy)

Wild boar foraging impacts the crops, pastures, and meadows causing remarkable losses to agricultural income. Protected areas located in plains, such as the Ticino Valley Natural Park, are characterized by the coexistence of important natural habitats and intensive agricultural areas. In the Park, from 2010 to 2017, 49% of the complaints report an event of damage to maize and 43% to meadows. The total expense for reimbursements of the maize amounted to € 439,341.52, with damages concentrated in May, after sowing period and between August and September, during the milky stage of maize. For meadows reimbursements amounted to € 324,768.66, with damage events concentrated in February and March. To reduce damage to crops, the Park administration carried out lethal control of the wild boar population. From 2006 to 2017, the most used control method was culling from hunting hides. In our analysis, we did not find significant relationships between the number of shot boars and the damage amount. The factors that determine the decrease of damage probability to crops are mainly related to human disturbance and the characteristics of the fields. The predictive model of damage risk built comparing damaged and undamaged fields showed a good predictive ability. The population viability analyses showed that it is impossible to obtain a drastic reduction of population with the current harvest rate. By tripling it and focusing on the females and sub-adult a numerical reduction of 50% of the population would be achievable in 7 years and the probability of population survival would be halved in 3 years.

Spatial structure of boreal woodland caribou populations in northwest Canada

Local population units (LPUs) were delineated in Canada’s recovery strategy for threatened boreal woodland caribou (Rangifer tarandus caribou). Population viability analyses central to contemporary integrated risk assessments of LPUs implicitly assume geographic closure. Several LPUs in northwest Canada, however, were in part delineated by geopolitical boundaries and/or included large areas in the absence of evidence of more finely resolved population spatial structure. We pooled >1.2 million locations from >1200 GPS or VHF-collared caribou from northeast British Columbia, northwest Alberta and southwestern Northwest Territories. Bayesian cluster analysis generated 10 alternative candidate LPUs based on a spatial cluster graph of the extent of pairwise co-occurrence of collared caribou. Up to four groups may be artifacts in as yet under-sampled areas. Four were mapped LPUs that were conserved (Prophet, Parker, Chinchaga and Red Earth). One small group between Parker and Snake-Sahtaneh known locally as the “Fort Nelson core,” and outside any mapped LPU, was also conserved. Finally, one large group, at >136000 km2, spanned all three jurisdictions and subsumed all of six delineated LPUs (Maxhamish, Snake-Sahtaneh, Calendar, Bistcho, Yates, Caribou Mountains) and part of southern Northwest Territories. These results suggest less geographic closure of LPUs than those currently delineated, but further analyses will be required to better reconcile various sources of knowledge about local population structure in this region.

Demographic reconstruction from ancient DNA supports rapid extinction of the great auk

The great auk was once abundant and distributed across the North Atlantic. It is now extinct, having been heavily exploited for its eggs, meat, and feathers. We investigated the impact of human hunting on its demise by integrating genetic data, GPS-based ocean current data, and analyses of population viability. We sequenced complete mitochondrial genomes of 41 individuals from across the species’ geographic range and reconstructed population structure and population dynamics throughout the Holocene. Taken together, our data do not provide any evidence that great auks were at risk of extinction prior to the onset of intensive human hunting in the early 16th century. In addition, our population viability analyses reveal that even if the great auk had not been under threat by environmental change, human hunting alone could have been sufficient to cause its extinction. Our results emphasise the vulnerability of even abundant and widespread species to intense and localised exploitation.

Applications to conservation biology

This chapter describes how models can aid in managing populations to prevent extinction, given uncertainty about their state. From previous chapters, it is clear that avoiding extinction requires keeping both abundance and the replacement rate high. However, for both, the question remains, how high? The question of how high abundance should be to achieve a certain risk is addressed by existing population viability analyses (PVA). By contrast, the problem of maintaining high replacement has received little attention. This chapter describes how uncertainty in population parameters and the frequency spectrum of the environment both affect estimates of the probability of extinction, including examples of PVAs that pay greater attention to those complications. Additionally, an example is provided of tracking both abundance and replacement to avoid extinction for many different populations of a single taxon, Pacific salmon. Finally, the role of portfolio effects (diversity in variance among populations) is explored.

Towards a predictive conservation biology: the devil is in the behaviour

One of the most important challenges in conservation biology is to predict the viability of populations of vulnerable and threatened species. This requires that the demographic stochasticity strongly affecting the ecological and evolutionary dynamics of especially small populations is correctly estimated and modelled. Here, we summarize theoretical evidence showing that the demographic variance in population dynamics is a key parameter determining the probability of extinction and also is directly linked to the magnitude of the genetic drift in the population. The demographic variance is dependent on the mating system, being larger in a polygynous than in monogamous populations. Understanding factors affecting intersexual differences in mating success is therefore essential in explaining variation in the demographic variance. We hypothesize that the strength of sexual selection, for example, quantified by the Bateman gradient, may be a useful predictor of the magnitude of the demographic stochasticity and hence the genetic drift in the population. We provide results from a field study of moose that support this claim. Thus, including central principles from behavioural ecology may increase the reliability of population viability analyses through an improvement of our understanding of factors affecting stochastic influences on population dynamics and evolutionary processes. This article is part of the theme issue ‘Linking behaviour to dynamics of populations and communities: application of novel approaches in behavioural ecology to conservation’.

Estimating observer error and steelhead redd abundance using a modified Gaussian area-under-the-curve framework

This study examined how a suite of habitat and environmental variables relate to the ability of a stream surveyor to identify (observer efficiency) and distinguish (observer accuracy) steelhead (Oncorhynchus mykiss) redds from other stream features. Two existing spawning survey protocols that included one or two redd observers were used to develop models to estimate redd observer error. In most cases, steelhead redd abundances using raw redd counts were underestimated. Mean annual rates of observer efficiency ranged from 0.44 to 0.57, and observer accuracy ranged from 0.67 to 0.83. Regardless of the observer error model used, adjusted annual redd abundance estimates were generally unbiased (range 1.6–0.6 redds). A Gaussian area-under-the-curve methodology that incorporates redd count data and observer error rates was used to generate unbiased estimates of steelhead redd abundance in the Wenatchee (170 redds, coefficient of variation (CV) = 44%) and Methow (106 redds, CV = 41%) rivers. Unbiased estimates of redd abundance will help inform new population viability analyses to better prioritize those populations with the greatest conservation need.