The ecology and management of mammal invasions in forests

Fumigant toxicity and behavioral alterations of six plant essential oils against the red fire ant (Solenopsis invicta Buren)

The red imported fire ant (RIFA), Solenopsis invicta Buren (Hymenoptera: Formicidae), is an invasive species that is considered to be among the 100 most dangerous species to human health and the environment. RIFA is currently controlled primarily by chemical insecticides. However, human health concerns and environmental problems require environment friendly, green insect pest control technology. In this study, the HS-SPME-GC/MS method was used to determine the volatile components of six essential oils, namely Illicium verum Burm, Blumea balsamifera (L.) DC., Citrus limon Burm, Acorus tatarinowii Schott, Mosla chinensis Maxim, and Cinnamomum cassia Presl, as well as their fumigation activity against RIFA. D-Limonene was identified as a core volatile in all six essential oils. The effects of volatile substances from essential oils on the fumigation activity and behavior of RIFA workers were studied by closed fumigation method. Except for C. limon essential oil, all other five plant essential oils exhibit excellent fumigation activity under the treatment of a concentration at 10 μL/ cm³ within 24 h. All plant essential oils are capable of causing the death of all red fire ants, while C. limon essential oil exhibited the lowest fumigation activity at 63.25%. Significant reductions in RIFA aggregation, aggressiveness, and gripping abilities were observed with all plant essential oils, and antenna sensilla appeared to bend or break. Moreover, after treating red ant fire ants with essential oil for 24 h, three protective enzyme activities were assessed. All six plant essential oils were shown to have enhanced enzyme activities for superoxide dismutase (SOD), glutathione S-transferase (GST), and catalase (CAT). It has been shown that plant essential oils have the capability of reducing the viability of red fire ants via receptor and behavioral factors, ultimately causing them to die off. As a conclusion, plant oils were demonstrated to be negatively affecting RIFA and providing a green and environmentally sustainable control method in this study.

Predicting the Potential Distribution of Non-Native Mammalian Species Sold in the South African Pet Trade

The pet trade is one of the main pathways of introduction of several mammals worldwide. In South Africa, non-native mammalian species are traded as pets, and so far, only four of these species are considered invasive. We used a list of 24 companion mammalian species compiled from a previous study. We selected a subset of 14 species for species distribution modeling (SDM) based on their trade popularity, invasion history and potential economic and socio-economic impacts. We aimed to estimate their potential distribution using their distribution records. Our SDM indicated that climate in South Africa was suitable for most traded species. However, commonly and easily available species had the broadest areas of suitable climates, such as house mice (Mus musculus) and Norwegian rats (Rattus norvegicus). In addition, the model with a human footprint suggested a high risk of invasion for Norwegian rats but less for house mice distribution. This assessment suggests the need of strict trade regulations and management strategies for pet mammals with broader suitability, which are already invasive, and most available for sale. In addition, our results provide a baseline approach that can be used to identify mammalian pet species with a potential risk of invasion so that urgent preventive measures can be implemented.

Mapping the status of the North American beaver invasion in the Tierra del Fuego archipelago

Quantifying the presence and environmental impact of invasive species is the starting point for research on management and nature conservation. North American beavers (Castor canadensis) were introduced to Argentina from Canada in 1946, and the species has been identified as a major agent of environmental change in the Tierra del Fuego archipelago in the Anthropocene. We studied the invasion status (distribution and density) of beavers through analyses of the dam densities in the Tierra del Fuego landscapes. We identified beaver dams with a GIS using visual interpretation of high-resolution aerial imagery from Microsoft Bing, Google Earth and HERE and related them to natural environmental gradients. These factors comprised geographic (vegetation zones and distance to streams), climatic (temperature, precipitation, evapotranspiration and net primary productivity) and topographic (elevation and slope) data. The datasets (dams and factors) were combined, and the data from the different zonation classes were subsequently compared using ANOVAs and Tukey's mean comparison tests. Deviations from the mean density (x mean density-x total mean density) were calculated to visualize the deviations for the studied factors. The datasets were also evaluated using principal component analyses (PCA). Our results showed a total of 206,203 beaver dams (100,951 in Argentina and 105,252 in Chile) in the study area (73,000 km2). The main island of Tierra del Fuego presented a greater degree of invasion (73.6% of the total study area) than the rest of the archipelago, especially in areas covered by mixed-evergreen and deciduous forests. The studied geographic, climatic and topographic factors showed positive trends (higher beaver preference) with beaver spread, which were all significant (p <0.05) when compared across the landscape. Although beavers are flexible in their habitat use, our empirical records showed that they had marked preferences and were positively influenced by the most productive forests. Here, we describe a scientific panorama that identified the drivers of species invasion based on satellite data and the available ecological datasets. The identification of such drivers could be useful for developing new tools for management and/or control strategies of the beavers in the Tierra del Fuego archipelago.

Efficacy and Animal Welfare Impacts of Novel Capture Methods for Two Species of Invasive Wild Mammals in New Zealand

All capture methods impose animal welfare impacts, but these impacts are rarely quantified or reported. We present data from two wildlife capture studies that trialled new methods for capturing Bennett's wallabies (Notamacropus rufogriseus) and red deer (Cervus elaphus) in New Zealand. We used helicopter net-gunning for both species, and compared this method with ground-based netting for wallabies and helicopter darting for red deer, using, for the first time in New Zealand, the fast-acting opioid thiafentanil. Efficacy and animal welfare parameters quantified were duration of handling and recovery, and frequency of adverse events, including escape, injury, and mortality. Cost-effectiveness was quantified for each method. Capture mortalities occurred for all methods for both species. For red deer, chemical immobilisation led to fewer traumatic injuries and fewer mortalities, while for wallabies, net-gunning led to fewer mortalities. Net-gunning was an efficient capture method for deer in open habitat, but led to the escape of 54% of wallabies and one wallaby mortality (4%). Ground-based netting resulted in the mortality of 17% of wallabies at the time of capture, and the capture of non-target species. The cost per captured wallaby was 40% more expensive for net-gunning (NZ$1045) than for ground-based netting (NZ$745), but, once corrected for mortalities at the time of capture and suitability of individuals for GPS-collar deployment, this was reduced to 29% and 12% more expensive, respectively. Net-gunning for red deer resulted in the escape of 13% of animals and mortality of 10% of animals at the time of capture. Helicopter-based darting for red deer using thiafentanil (c. 0.03-0.06 mg/kg) had high capture efficacy (zero escapes), rapid induction times (mean of 3 min), and a low mortality rate at 14 days post-capture (3%), but it was more expensive per deer captured and collared than aerial netting (NZ$2677 and NZ$2234, respectively). We recommend reporting of adverse event data for all wildlife capture techniques to permit continual refinement of field methods.