Modelling the damage costs of invasive alien species

The rate of biological invasions is growing unprecedentedly, threatening ecological and socioeconomic systems worldwide. Quantitative understandings of invasion temporal trajectories are essential to discern current and future economic impacts of invaders, and then to inform future management strategies. Here, we examine the temporal trends of cumulative invasion costs by developing and testing a novel mathematical model with a population dynamical approach based on logistic growth. This model characterises temporal cost developments into four curve types (I–IV), each with distinct mathematical and qualitative properties, allowing for the parameterization of maximum cumulative costs, carrying capacities and growth rates. We test our model using damage cost data for eight genera (Rattus, Aedes, Canis, Oryctolagus, Sturnus, Ceratitis, Sus and Lymantria) extracted from the InvaCost database—which is the most up-to-date and comprehensive global compilation of economic cost estimates associated with invasive alien species. We find fundamental differences in the temporal dynamics of damage costs among genera, indicating they depend on invasion duration, species ecology and impacted sectors of economic activity. The fitted cost curves indicate a lack of broadscale support for saturation between invader density and impact, including for Canis, Oryctolagus and Lymantria, whereby costs continue to increase with no sign of saturation. For other taxa, predicted saturations may arise from data availability issues resulting from an underreporting of costs in many invaded regions. Overall, this population dynamical approach can produce cost trajectories for additional existing and emerging species, and can estimate the ecological parameters governing the linkage between population dynamics and cost dynamics

Premières données de l’étude par radio-pistage VHF des déplacements des chats dans un site majeur de reproduction du Puffin Yelkouan, endémique de Méditerranée

Le chat représente un des prédateurs invasifs les plus menaçants pour les espèces natives des îles et particulièrement pour les oiseaux marins adultes qui sont fortement vulnérables à la prédation. Les populations du Puffin Yelkouan, espèce endémique du bassin méditerranéen, sont réparties en quelques grandes colonies de reproduction et sont en voie de déclin, notamment du fait de l’impact des chats harets et errants. Dans une étude précédemment publiée, l’impact des chats introduits sur la population de puffins de l’île du Levant a été évalué au travers du régime alimentaire du chat sur une période de deux ans. Cette étude a mis en évidence que les chats consommaient trois proies principales : le Lapin, le Rat noir et le Puffin Yelkouan, et qu’un pic de prédation de puffins était observé dès leur arrivée sur les colonies (période de prospection). Nous avons donc cherché à compléter ce travail par une étude préliminaire visant à étudier les patrons de mouvement de quatre chats (trois chats harets et un chat domestique) via un suivi VHF (very high frequency), dans le but d’analyser leurs comportements individuels et leurs domaines vitaux sur l’île du Levant, qui est l’un des principaux sites de reproduction du Puffin Yelkouan. Nos résultats montrent que deux des trois chats harets ont été détectés dans les colonies de puffins durant les périodes de prospection et de reproduction de cet oiseau marin alors que le chat domestique n’a jamais été détecté dans ces colonies. Cela suggère que les patrons de déplacement des quatre chats suivis puissent être liés à la présence des puffins dès que ces oiseaux marins arrivent à la colonie. Les chats suivis montrent des domaines vitaux de taille relativement réduite, plus larges pour les chats harets qui couvrent de plus grandes distances, et avec des territoires chevauchants, que pour le chat domestique. Ces résultats préliminaires de patrons de déplacements, couplés aux résultats précédents de prédation du chat sur le Puffin Yelkouan, nous indiquent que l’impact du chat haret se doit d’être limité. Cet objectif doit être atteint en effectuant une stratégie de gestion efficace qui tiendrait compte des patrons de déplacements des chats afin d’éviter l’épuisement d’un des sites de reproduction les plus importants pour cette espèce de puffin endémique de MéditerranéeCats are considered one of the most harmful invasive predators of island native species, particularly adult shearwaters, which are highly vulnerable to predation. Populations of Yelkouan shearwater, an endemic species of the Mediterranean basin with only a few large breeding colonies, are predicted to decline in response to feral or free-roaming cats. In a previous study, the impact of introduced cats on the Yelkouan shearwater population of Le Levant Island was assessed through the analysis of cat diet over a two-year period. The study showed that cats prey upon three staple species: rabbits, rats, and shearwaters, with a peak of predation on shearwaters immediately upon their arrival at colonies (prospecting period). Here, we supplement this previous work by conducting a preliminary study on the movement patterns of four free-roaming cats (three feral and one domestic) using very high frequency (VHF) tracking to analyse individual behaviour and home ranges on Le Levant Island, one of the Yelkouan shearwater’s major breeding sites. Our results show that two of the three feral cats were recorded inside and in close vicinity to the shearwater colonies, mainly during the prospecting period, while the domestic cat was never recorded inside the colonies. This suggests that some feral cats could show movement behavioural patterns linked to the shearwater presence as soon as these seabirds arrive at the colonies. The monitored domestic cat also showed a relatively small home range, while feral cats covered larger distances and with overlapping territories. Based on these preliminary results of cat movement behaviour, in addition to the previous results of cat predation, it is evident that cat impact must be reduced. This may be achieved through accurate management strategy that takes cat movement behaviour into account to avoid exhausting one of the most important breeding sites for this Mediterranean endemic specie

Invasion Biology: Specific Problems and Possible Solutions

International audienceBiological invasions have been unambiguously shown to be one of the major global causes of biodiversity loss. Despite the magnitude of this threat and recent scientific advances, this field remains a regular target of criticism – from outright deniers of the threat to scientists questioning the utility of the discipline. This unique situation, combining internal strife and an unaware society, greatly hinders the progress of invasion biology. It is crucial to identify the specificities of this discipline that lead to such difficulties. We outline here 24 specificities and problems of this discipline and categorize them into four groups: understanding, alerting, supporting, and implementing the issues associated with invasive alien species, and we offer solutions to tackle these problems and push the field forward

Human-cat relationship in an oceanic biosphere reserve: the case of La Palma Island, Canary archipelago

Removal of feral cats from island environments is a useful mechanism by which their ecological impact on endangered species can be reduced or ended. Nevertheless, because cats are anthropogenic in their origins, social perceptions of management practices play a large role in their implementation. Four-hundred questionnaires were delivered (386 were returned) with 100 going to each of the following: local residents; environmental workers; tourists; and, hunters. Questions explored respondents’ knowledge about island biodiversity and invasive species as well as attitudes towards cat population management methods. Habitat destruction and introduction of invasive species were considered the main threats for the conservation of island biodiversity. Most respondents considered cats to have a negative impact on biodiversity and sterilization campaigns were considered most appropriate for cat population control. Several free sterilization campaigns have been conducted in La Palma Island Biosphere Reserve in order to reduce free-ranging cats and were well received by local people. This research, which combined concepts of management, ecology and social sciences, provides valuable insights which may to be applicable on several other islands where cats and people are present and in conflict with conservation priorities

Future directions in conservation research on petrels and shearwaters

Shearwaters and petrels (hereafter petrels) are highly adapted seabirds that occur across all the world's oceans. Petrels are a threatened seabird group comprising 124 species. They have bet-hedging life histories typified by extended chick rearing periods, low fecundity, high adult survival, strong philopatry, monogamy and long-term mate fidelity and are thus vulnerable to change. Anthropogenic alterations on land and at sea have led to a poor conservation status of many petrels with 52 (42%) threatened species based on IUCN criteria and 65 (52%) suffering population declines. Some species are well-studied, even being used as bioindicators of ocean health, yet for others there are major knowledge gaps regarding their breeding grounds, migratory areas or other key aspects of their biology and ecology. We assembled 38 petrel conservation researchers to summarize information regarding the most important threats according to the IUCN Red List of threatened species to identify knowledge gaps that must be filled to improve conservation and management of petrels. We highlight research advances on the main threats for petrels (invasive species at breeding grounds, bycatch, overfishing, light pollution, climate change, and pollution). We propose an ambitious goal to reverse at least some of these six main threats, through active efforts such as restoring island habitats (e.g., invasive species removal, control and prevention), improving policies and regulations at global and regional levels, and engaging local communities in conservation efforts

Biological Invasions 2020 Horizon

This special issue points to the necessity to continue actively working on biological invasions, as invasive species remain a main and global threat for biodiversity through a global homogenization process. This issue includes six research papers, covering a large range of taxa, studying new invasive processes and proposing innovative management solutions. The way forward will be to continue working in close relation with other stakeholders and decision-makers, increase communication efforts, solicit societal feedback, and quickly implement consistent legislation

Le Chat haret

Le Chat hare

Ecologie trophique et impact d'un prédateur introduit (Felis silvestris catus) dans les écosystèmes insulaires

Les invasions biologiques sont la première cause de perte de biodiversité dans les écosystèmes insulaires. Les chats, prédateurs introduits sur les îles, s'alimentent sur une grande variété de proies. Ainsi, les chats menacent d'extinction au moins 167 espèces de vertébrés sur 123 îles de la planète, et sont impliqués dans l'extinction d'au moins 32 taxa. Sur l'archipel des îles d'Hyères, le régime alimentaire de ce prédateur est constitué principalement de mammifères introduits et d'oiseaux. Le rat, le lapin et le puffin yeikouan, oiseau marin endémique du bassin Méditerranéen, représentent à elles seules 90% de la biomasse totale ingérée par le chat. La prédation du chat sur le puffin s'est avérée forte et récurrente L'impact du chat a été évalué en utilisant des modèles démographiques matriciels. Soumise à une telle prédation, la petite population de puffin de Port-Cros ne peut se maintenir que par l'apport d'oiseaux immigrants. Cette menace forte a motivé une campagne d'éradication du chat sur l'île de Port-Cros entraînant une tendance à la hausse de la population de puffin sans apparition du phénomène de relâche de mésoprédateursAIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocSudocFranceF

Underlying impacts of invasive cats on islands: Not only a question of predation

The domestic cat has been introduced on most islands worldwide, where it has established feral populations and is currently known to be one of the worst invasive mammalian predators. Predation is the strongest deleterious effect of cats on wildlife, inducing a direct negative impact on population size and dynamics, breeding success and changes in species assemblages. Direct predation is not the only damaging impact on native wildlife, since cats can be responsible for other poorly-documented underlying ecological impacts, like competition, hybridization, disease transmission, ecological process alteration, and behavioral change. Here, we pinpoint relevant examples of these ecological impacts, by searching for accurate data from published literature. We used electronic databases covering most of the world islands where the effects of cats were documented. Knowledge of these impacts can be of great importance to preserve insular ecosystem functions and persistence of endangered native species. We emphasize that direct predation processes should not be the only factor considered in the management of invasive cats on islands.This work was supported by several European Union projects: CGL-2004-0161 BOS co-financed by the Spanish Ministry of Science and Education, the French FRB (DREAMS project) and PEPS-CNRS programme.Peer Reviewe

Influence of the number of queens on nest establishment: native and invasive ant species

Simple Summary : Nest establishment is a critical stage of the ant life cycle because it determines the chances of colony success. Here, we study the effect of different numbers of queens (i.e., one or six) on the position of queens and workers inside and outside the artificial nests of an invasive (Linepithema humile) and Mediterranean native (Tapinoma nigerrimum) species. Our results suggest that queens in nests with six queens entered the nest faster than single queens. Similarly, during nest establishment, workers in nests with six queens entered the nest faster, with this effect being more pronounced for the native species. Once nests were established, fewer workers were engaged in outside-nest tasks in nests with six queens. This was especially true for workers of the native species engaged in patrolling. These results suggest that the number of queens can influence both queen and worker behavior, and that invasive and native species have different responses.Abstract : As a critical stage in the life cycle of ant colonies, nest establishment depends on external and internal factors. This study investigates the effect of the number of queens on queen and worker behavior during nest establishment in invasive Argentine ants (Linepitema humile) and native Mediterranean Tapinoma nigerrimum. We set up experimental colonies with the same number of workers but with one or six queens. At different time points, we recorded the positions of queens and workers inside and outside the nest. Our results highlight the influence of the number of queens on the position of queens and workers with between-species differences. Queens of both species entered the nests more quickly when there were six queens. During nest establishment, more workers were inside nests with six queens for both species, with this effect being greater for T. nigerrimum. Once nests were established, fewer workers of both species were engaged in nest maintenance and feeding in nests with six queens; T. nigerrimum had fewer workers engaged in patrolling. These results suggest that the number of queens is a key factor driving queen and worker behavior during and after nest establishment with different species responses