Impact of the introduced small Indian mongoose (Herpestes auropunctatus) on abundance and activity time of the introduced ship rat (Rattus rattus) and the small mammal community on Adriatic islands, Croatia

The small Indian mongoose (Herpestes auropunctatus) is one of the world’s 100 worst invasive species (IUCN 2000). It has negative impacts on several small mammals on islands where it was introduced. We assess the abundance of small mammal populations and the activity time of introduced ship rats (Rattus rattus) on three mongoose-infested and three mongoose-free islands in the Adriatic Sea, Croatia. We set up three transects on each island with a trapping system consisting of 30 small live traps to capture small mammals under 30 grams and 30 larger traps to capture ship rats and mongooses, on each transect. Our results support an already large but mostly speculative literature that suggests inability of the small Indian mongoose to reduce high abundances of introduced R. rattus. Further, we suggest that the low abundance of native small mammals is probably not solely caused by the mongoose but also by high R. rattus populations on all six islands. In addition, we provide evidence that R. rattus has changed its activity time to become more nocturnal on mongoose-infested islands, possibly to avoid predation by the mongoose. As R. rattus became more nocturnal, the diurnal mongoose may have become the main predator on amphibians, reptiles, and poultry

Biological invasions: Much progress plus several controversies

La biologia de les invasions ha permès avançar en la comprensió de les invasions i de la capacitat per gestionar-les. La recerca recent s'ha centrat sobretot en les invasions que afecten ecosistemes sencers. La genètica molecular ha revelat la generalització relativa d'hibridacions entre espècies introduïdes i natives, i entre poblacions genèticament diferents introduïdes en una mateixa regió. Les controvèrsies sobre els resultats de la biologia de les invasions i de la seva gestió són: I) L'afirmació que la majoria d'invasions causen poc impacte, encara que hagin estat poc estudiades. II) L'argument que les invasions poden augmentar la biodiversitat local, sense reconèixer que disminueixen la biodiversitat global. III) L'afirmació que la biologia de les invasions és una forma de xenofòbia, restant importància al fet que la lluita contra les espècies invasores està motivada pels seus impactes negatius. IV) La creença que hi ha poc que puguem fer per prevenir o controlar les invasions, fent cas omís de l'éxit dels projectes d'eradicació i gestió i de nous enfocaments prometedors. V) Les objeccions dels defensors dels drets dels animals a la gestió dels vertebrats, particularment mamífers, sent aquest un problema que no es resoldrà fàcilment.Invasion biology has allowed to progress in our understanding of invasions and our ability to manage them. Recent research has largely focused on invasions that impact entire ecosystems. Molecular genetics has revealed the relative commonality of hybridizations between introduced and native species and between genetically different populations introduced into the same region. Controversies surrounding the findings of invasion biology and management include: I) The claim that most invasions are inconsequential, even if they have been scarcely studied. II) The argument that invasions can increase local biodiversity, without recognizing that they decrease global biodiversity. III) The statement that invasion biology is a form of xenophobia, downplaying evidence that fighting invasive species is motivated by their negative impacts. IV) The belief that there is little we can do to prevent or control invasions, ignoring successful eradication and management projects and promising novel approaches. V) Animal rights objections to the management of invasive vertebrates, particularly mammals, which reflects different philosophical stances and will not be easily resolved

Disparate responses of above- and belowground properties to soil disturbance by an invasive mammal

Introduced mammalian herbivores can negatively affect ecosystem structure and function if they introduce a novel disturbance to an ecosystem. For example, belowground foraging herbivores that bioturbate the soil, may alter process rates and community composition in ecosystems that lack native belowground mammalian foragers. Wild boar (Sus scrofa) disturb the soil system and plant community via their rooting behavior in their native range. Given their size and the numbers in their populations, this disturbance can be significant in forested ecosystems. Recently, wild boar were introduced to Patagonian forests lacking native mammalian herbivores that forage belowground. To explore how introduced wild boar might alter forested ecosystems, we conducted a large-scale wild boar exclusion experiment in three different forest types (Austroducedrus chilensis forest, Nothofagus dombeyi forest, and shrublands). Wild boar presence altered plant composition and structure, reducing plant biomass 3.8-fold and decreasing both grass and herb cover relative to areas where wild boar were excluded. Decomposition rates and soil compaction also declined by 5% in areas where boar had access; however, rooting had no effect on soil nutrient stocks and cycling. Interestingly, there were no differences in wild boar impacts on different forest types. We found that after 3-years of exclusion, belowground foraging by wild boar had a larger impact on plant community structure and biomass than it did on soil nutrient processes.Fil: Barrios Garcia Moar, Maria Noelia. Administración de Parques Nacionales. Delegación Regional Patagonia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Classen, Aimee T.. University of Tennessee; Estados UnidosFil: Simberloff, Daniel. University of Tennessee; Estados Unido

Causes of exotic bird establishment across oceanic islands

The probability that exotic species will successfully establish viable populations varies between regions, for reasons that are currently unknown. Here, we use data for exotic bird introductions to 41 oceanic islands and archipelagos around the globe to test five hypotheses for this variation: the effects of introduction effort, competition, predation, human disturbance and habitat diversity (island biogeography). Our analyses demonstrate the primary importance of introduction effort for avian establishment success across regions, in concordance with previous analyses within regions. However, they also reveal a strong negative interaction across regions between establishment success and predation; exotic birds are more likely to fail on islands with species-rich mammalian predator assemblages

Communication distance predicts territory size for an urban songbird

Many studies demonstrate that urban noise interferes with animal communication by masking acoustic signals such as birdsong, but the functional consequences of impaired communication are still not well understood. Although many bird species sing at higher amplitude in noise pollution, communication distance is still reduced in noisy urban soundscapes. Song is a long-distance signal that functions to attract a mate and defend a territory, so a reduction in communication distance could negatively influence a male’s reproductive or competitive success. Reduced territorial success could manifest as more frequent territorial intrusions, reduced territory quality, or reduced territory size. We examined the relationship between communication distance and territory size in white-crowned sparrows (Zonotrichia leucophrys) across an urban-rural gradient in the San Francisco Bay Area in Spring 2021. We mapped the territories of male White-crowned sparrows and calculated territory size as the 75% utilization distribution using a kernel density estimator. We measured the amplitude of each male’s songs as well as background and ambient noise levels on his territory, which we then used to calculate the communication distance of each song. We found the mean communication distance of each individual and assessed its relationship to territory size. the communication distance of a bird’s songs significantly predict his territory size, such that birds with shorter communication distance tend to have smaller territories. This suggests that communication distance may influence the size of songbird territories. In keeping with this trend, urban birds had significantly smaller territories than rural birds. This finding strengthens our understanding of the link between communication and its fitness-related functions – an important frontier in the study of birdsong. It also underlines the potential complexity of the impacts of the anthropogenic soundscape upon animal behavior

Nature’s nature and the place of non-native species The New Wild – Why Invasive Species Will Be Nature’s Salvation Fred Pearce (Beacon Press, Boston, US; 2015) ISBN: 978-0-8070-3368-5.

Unknow

Eco-Defense against Invasions

Characterizing patterns of invasion across space, time, and taxonomic group will help reveal how invasive species affect ecosystem function and individual native specie

Insular carnivore biogeography: island area and mammalian optimal body size.

Published versio

Body size of insular carnivores: little support for the island rule.

Published versio

Turnover dynamics of breeding land birds on islands: is island biogeographic theory ‘true but trivial’ over decadal time-scales?

The theory of island biogeography has revolutionised the study of island biology stimulating considerable debate and leading to the development of new advances in related areas. One criticism of the theory is that it is ‘true but trivial’, i.e., on the basis of analyses of annual turnovers of organisms on islands, it has been posited that stochastic turnover mainly comprises rare species, or repeated immigrations and extinctions thereof, and thereby contribute little to the overall ecological dynamics. Here, both the absolute and relative turnover of breeding land birds are analysed for populations on Skokholm, Wales, over census intervals of 1, 3, 6, 12, and 24 years. As expected, over short census intervals (≤6 years), much of the turnover comprised repeated colonisations and extinctions of rare species. However, at longer intervals (12 and 24 years), a sizeable minority of species (11% of the total recorded) showed evidence of colonisation and/or extinction events despite sizeable populations (some upwards of 50 pairs). These results suggest that a longer-term view is required to take into account turnover involving more common species