Habitat and Season Effects on Small Mammal Bycatch in Live Trapping

Trapping small mammals is frequently used to study the dynamics, demography, behavior and presence of pathogens. When only particular small mammal species are in the focus of interest, all other species are unnecessary bycatch. We analyzed data from extensive live trapping campaigns conducted over the last decade in Germany, following a consistent standard trapping protocol that resulted in about 18,500 captures of small mammals. Animals were trapped with Ugglan multiple capture traps in grassland, forest and margin habitat. Trap success and the proportion of bycatch were about 30% when target species were common voles (Microtus arvalis) in grassland and common voles and bank voles (Clethrionomys glareolus) in margins and forests. This was more pronounced in spring and along margins. Species mentioned in the early warning list according to the Red List Germany were higher in numbers and proportion in spring and in grassland. The results will help to avoid periods with enhanced presence of bycatch, including endangered species (if the purpose of the study allows) or to pay particular attention in certain seasons and habitats when the occurrence of bycatch is most likely.

Baiting/Luring Improves Detection Probability and Species Identification-A Case Study of Mustelids with Camera Traps

Simple Summary

Camera traps are now widely used in animal research because they can monitor animals continuously. Nocturnal mammals are particularly difficult to monitor, and identification without cameras would be difficult. However, camera traps can be improved. We here compared two experimental settings to increase detection and images taken of mustelids, mostly martens. Both tuna bait and glandular scents improved the detection and the number of images taken. Both methods were more successful than a control group setting without any attractants.

Abstract

Motion-triggered trail cameras (hereafter camera traps) are powerful tools which are increasingly used in biological research, especially for species inventories or the estimation of species activity. However, camera traps do not always reliably detect animal visits, as a target species might be too fast, too small, or too far away to trigger an image. Therefore, researchers often apply attractants, such as food or glandular scents, to increase the likelihood of capturing animals. Moreover, with attractants, individuals might remain in front of a camera trap for longer periods leading to a higher number of images and enhanced image quality, which in turn might aid in species identification. The current study compared how two commonly used attractants, bait (tuna) and glandular scent (mustelid mix), affected the detection and the number of images taken by camera traps compared to control camera sites with conventional camera traps. We used a before–after control group design, including a baseline. Attractants increased the probability of detecting the target species and number of images. Tuna experiments produced on average 7.25 times as many images per visit than control camera traps, and scent lures produced on average 18.7 times as many images per visit than the control traps.

Self-service traps inspected by avian and terrestrial predators as a management option for rodents

BACKGROUND

Worldwide, serval rodent species are major pests in agricultural landscapes. A vole-specific tub-trap combining trapping and natural predators was developed to minimize the migration of rodents into agricultural crops. The trap was tested in enclosures in terms of its trapability of common voles (Microtus arvalis Pallas) and in the field regarding predator access and removal of voles, both in comparison to a commercially available self-service trap (standby-box).

RESULTS

The trapability of voles was equal for tub-traps and standby-boxes. The removal of voles occurred four times more often from tub-traps by a wider variety of predators (e.g. smaller terrestrial predators, birds of prey). Visits by predators were most likely if study sites were not surrounded by artificial surfaces (70% visit probability by terrestrial predators) or if they were in areas that were more than 25% (semi)natural (95% visit probability by avian predators). Furthermore, visits by avian predators increased with time and a learning effect could be demonstrated for magpies (Pica pica L.). From the first to the fifth day, the visit probability of magpies quadrupled.

CONCLUSIONS

Visits by predators decreased with increasing cover of artificial surfaces or decreasing cover of (semi)natural areas, proving the importance of (semi)natural areas in the agricultural landscape. Long-term trials with different baiting techniques and in landscapes characterized by organic farming should be conducted to ensure the regular removal of voles. The use of tub-traps that are frequently visited by predators could support crop protection, which might limit the use of rodenticide and the associated exposure risk of non-target wildlife. © 2019 Society of Chemical Industry.

Can remote infrared cameras be used to differentiate small, sympatric mammal species? A case study of the black-tailed dusky antechinus, Antechinus arktos and co-occurring small mammals in southeast Queensland, Australia

The black-tailed dusky antechinus (Antechinus arktos) is an endangered, small carnivorous marsupial endemic to Australia, which occurs at low population density along with abundant sympatric populations of other small mammals: Antechinus stuartii, Rattus fuscipes and Melomys cervinipes. Using A. arktos as a model species, we aimed to evaluate the effectiveness of infrared digital camera traps for detecting and differentiating small mammals and to comment on the broad applicability of this methodology. We also sought to understand how the detection probabilities of our target species varied over time and characterize their activity patterns. We installed 11 infrared cameras at one of only three known sites where A. arktos occurs for five consecutive deployments. Cameras were fixed to wooden stakes and oriented vertically, 35 cm above ground, directly facing bait containers. Using this method, we successfully recorded and identified individuals from all four species of small mammal known previously in the area from live trapping, including A. arktos. This validates the effectiveness of the infrared camera type and orientation for small mammal studies. Periods of activity for all species were highly coincident, showing a strong peak in activity during the same two-hour period immediately following sunset. A. arktos, A. stuartii and M. cervinipes also displayed a strong negative linear relationship between detection probability and days since deployment. This is an important finding for camera trapping generally, indicating that routine camera deployment lengths (of one-to-two weeks) between baiting events may be too long when targeting some small mammals.

Camera traps provide insight into factors influencing trap success of the swamp wallaby, Wallabia bicolor

Trapping programs for mammals often have low capture success, which is known to be influenced by a range of environmental factors, in addition to aspects of the traps themselves. However, the behavioural responses to traps by the target species are largely unknown. We simultaneously set camera traps and soft-walled double-layered traps for swamp wallabies, Wallabia bicolor, and used images from the camera traps to investigate responses by the target species. Wallabies mostly visited traps after sunset, with the number of visits declining steadily through the night. Visits to traps were more frequent during crescent and new moon phases and when the moon was set. In the majority (59%) of these visits, wallabies did not enter the traps. In some cases wallabies consumed only the bait outside the trap, or the trap door had been closed, usually by other swamp wallabies or bobucks, Trichosurus cunninghami, but in many cases (28% of visits) we could not discern why wallabies failed to enter. When wallabies did enter traps, just 14% of visits resulted in successful capture, with non-captures mainly occurring because wallabies reached in to obtain bait without triggering the trap.

Standard Operating Procedures for aluminium box, wire cage, and pitfall trapping, handling, and temporary housing of small wild rodents and marsupials

Many researchers and educators need to provide Standard Operating Procedures (SOPs) to their Animal Ethics Committee (AEC) for the purpose of trapping, handling, and temporarily housing small mammals. We devised general SOPs that are compatible with most existing ones for Australia and had these SOPs reviewed by a panel of Australian experts. The SOPs may be used as guidelines by researchers who need to provide such protocols to their organisation or AEC, or in teaching.

There's no accounting for taste: bait attractants and infrared digital cameras for detecting small to medium ground-dwelling mammals

Context Reliable information about the occurrence and distribution of threatened forest-dwelling mammals is critical for developing effective conservation plans. To optimise limited resources, advances need to be made to the toolkit available for detecting rare and cryptic fauna. Aims We trialled three bait attractants (peanut butter with oats, live mealworms and black truffle oil) in combination with infrared digital cameras to determine whether detection rates of forest-dwelling native mammals in south-eastern Australia were influenced by: (1) bait type; (2) previous visits by conspecifics; (3) previous visits by Rattus; and (4) duration of bait deployment. Methods Bait attractants were set at 40 camera stations in combination with odourless controls. Over two fortnight-long deployments, 1327 images were captured of 22 mammal and bird species. From these data, detailed statistical analyses were conducted of six mammal genera. Key results Peanut butter with oats was found to be a significantly better attractant than empty bait holders for Antechinus, Isoodon, Perameles and Rattus, but not for Potorous or Pseudocheirus. Truffle oil and mealworms were also significantly better attractants than the control for Rattus but not the other five genera. When Antechinus, Isoodon, Potorous or Rattus were detected at a bait station there was a significant likelihood they had been detected there during the previous 24 h. This was not the case for Perameles or Pseudocheirus. A prior visit by Rattus to a station had no significant influence on the detection probabilities of Antechinus, Isoodon, Perameles, Potorous and Pseudocheirus during the subsequent 24 h. Detection probabilities for Isoodon and Rattus declined significantly during the fortnight-long deployments but trends for the other genera were not significant. Conclusions Peanut butter with oats is an excellent general purpose bait for detecting small to medium-sized mammals. However, scope exists for using other baits to target species. For example, truffle oil baits may reduce by-catch of non-target Rattus in labour intensive cage trapping of bandicoots. Regardless of bait type, longer deployments are necessary to detect Perameles, Potorous or Pseudocheirus than Antechinus, Isoodon or Rattus. Implications Targeted detection of predominantly ground-dwelling mammals may be improved by better understanding the attraction of species to baits and required bait deployment times.

Effects of drought on weight, survival and breeding success of agile antechinus (Antechinus agilis), dusky antechinus (A. swainsonii) and bush rats (Rattus fuscipes)

Extreme weather conditions, such as drought, significantly decrease the survival and breeding success of numerous species. Despite the frequent occurrence of such conditions in Australia, little is known about the effects of changing environmental conditions on the native small mammals. This study, conducted from 2002 to 2004, focussed on sympatric wild populations of the agile antechinus (Antechinus agilis), with more limited information on the dusky antechinus (A. swainsonii) and the bush rat (Rattus fuscipes). Bodyweights of agile antechinus before and during the breeding season were significantly lower in 2003 (drought) than in 2002 or 2004. Survival of female agile antechinus and the number of young per litter also decreased significantly during drought. In contrast, the dusky antechinus showed no difference in mean bodyweights between years, high survival rates of females and similar litter sizes in 2002 and 2003. There was also no difference in bodyweight of bush rats between years. Low rainfall was recorded during pregnancy and lactation in the agile antechinus, but rainfall was higher during pregnancy and lactation in the dusky antechinus. The survival and breeding success of the agile antechinus may have been adversely affected by a combination of interspecific competition, timing of the breeding season and severity of the drought.

Using multiple survey methods to detect terrestrial reptiles and mammals: what are the most successful and cost-efficient combinations?

The selection of methods for wildlife surveys is a decision that will influence the accuracy and comprehensiveness of survey outcomes. The choice of methods is commonly based on the species of interest, yet is often limited by the project budget. Although several studies have investigated the effectiveness of various survey techniques for detecting terrestrial mammal and reptile species, none have provided a quantitative analysis of the costs associated with different methods. We compare the detection success and cost efficiency of cage traps, Elliott traps, pit-fall traps, hair funnels, direct observation, and scat detection/analysis for detecting the occurrence of terrestrial reptile and small mammal species in urban bushland remnants of Brisbane City, Queensland, Australia. Cage traps and Elliott traps coupled with hair funnels were the most cost-effective methods for detecting the highest number of ground-dwelling mammal species. Pit-fall traps and direct observations were the most cost-effective methods for maximising the number of reptile species identified. All methods made a contribution to overall detection success by detecting at least one species not detected by any other method. This suggests that a combination of at least two complementary methods will provide the most successful and cost-efficient detection of reptile and mammal species in urban forest remnants. Future studies should explicitly test these findings and examine efficient trapping combinations across different habitat types and for other fauna groups.