Influence of Nesting Material Composition on Tick Tube Use by Peromyscus leucopus

Host-targeted acaricides are a valuable tool for the reduction of ticks and tick-borne disease. Tick tubes (also known as tick control tubes) are commercially available products containing permethrin-treated nesting materials. Through superficial acaricide application to Peromyscus mice, tick tubes reduce populations of the blacklegged tick, Ixodes scapularis Say. Results of prior field trials have varied, suggesting that mouse behavior as well as the scale of the intervention and the composition of the local host community are important determinants of efficacy. Here we evaluated behaviors related to nest material collection by P. leucopus. Two forms of nest materials used in commercial tick tube products (cotton batting and balls) were assessed through side-by-side comparisons over a four-week period. We quantified cotton uptake by monitoring weekly changes in material weight and used video surveillance to categorize and assess mouse behaviors. The odds of cotton batting being taken from tubes was 2.14 times greater than cotton balls but the process was less efficient; mice removed 0.35 g less cotton batting for each removal event and required 2.17 times longer to complete the removal. While cotton balls were readily carried in the jaws of mice, batting required separating smaller fragments from the mass before placement in the oral cavity. Video surveillance suggested that a small number of mice were super users and responsible for 22% of the 119 visits in which material was removed. Combined, material weight loss and video-captured removal events improve our understanding of host usage of nest materials but also raise questions about dissemination of the material in nests of the local mouse community.

The Effect of Early Life Stress on Emotional Behaviors in GPR37KO Mice

GPR37 is an orphan G-protein-coupled receptor, a substrate of parkin which is linked to Parkinson’s disease (PD) and affective disorders. In this study, we sought to address the effects of early life stress (ELS) by employing the paradigm of limited nesting material on emotional behaviors in adult GPR37 knockout (KO) mice. Our results showed that, while there was an adverse effect of ELS on various domains of emotional behaviors in wild type (WT) mice in a sex specific manner (anxiety in females, depression and context-dependent fear memory in males), GPR37KO mice subjected to ELS exhibited less deteriorated emotional behaviors. GPR37KO female mice under ELS conditions displayed reduced anxiety compared to WT mice. This was paralleled by lower plasma corticosterone in GPR37KO females and a lower increase in P-T286-CaMKII by ELS in the amygdala. GPR37KO male mice, under ELS conditions, showed better retention of hippocampal-dependent emotional processing in the passive avoidance behavioral task. GPR37KO male mice showed increased immobility in the forced swim task and increased P-T286-CaMKII in the ventral hippocampus under baseline conditions. Taken together, our data showed overall long-term effects of ELS—deleterious or beneficial depending on the genotype, sex of the mice and the emotional context.

Birds using artificial plants as nesting material

Here we present the first cases of birds using artificial plants as nest material. We report our findings for the common coot (Fulica atra) from Leiden, the Netherlands, in 2019. This is the first population of freshwater birds studied for its use of anthropogenic nest materials, and together with another report from the same year, the earliest case of an entire bird population with plastic in all nests. We also report the first artificial plants used as nesting material by birds, and discuss the implications of their usage as such.

Daily Patterns of Foraging and Aggressive Behaviors in Great-tailed Grackle (Quiscalus mexicanus) at an Urban Patch with Availability or Absence of Resources

The Great-tailed Grackle (Quiscalus mexicanus) seems to take advantage of inhospitable environments such as cities. However, it is not yet fully understood how these birds exploit hostile environments to their advantage. Casual observation suggests that this species can obtain resources of biological importance such as food or nesting material from the garbage. As a first approach to the problem, we located a patch outside a residential building in a high-density urban area, where the residents left their trash for pickup. A group of wild Great-tailed grackles was identified as regular visitors. In total, 25 days were recorded at the site (November 2017 - January 2018). Events such as foraging, the number of subjects present at the foraging area, aggressive behaviors between members of the group, and their relation with the presence or absence of the garbage collector truck were registered. The results show a higher number of grackles at the observation site and a higher frequency of foraging behaviors in the presence of garbage collection than in its absence. In its presence, the distribution of foraging during the day follows a normal distribution. In the absence, the distribution shows more variability towards the day. The highest frequency of interactions occurred between two grackles, yet there were records of up to eight subjects. The highest number of aggressions registered took place in the absence of garbage collection than in its presence. Moreover, the focal subject exhibits fewer agonistic behaviors than other group members, a result expected if the producer-scrounger game literature is considered. The outcome is explained in terms of deprivation and availability of resources. Finally, we conclude that grackles can exploit hazardous environments such as cities due to the highly social behaviors exhibited during foraging.

The effects of COVID-19 litter on animal life

During the COVID-19 pandemic, Personal Protective Equipment (PPE) is massively used, resulting in a new wave of litter: protective face masks and gloves. Here we present the first case of a fish entrapped in a medical glove, encountered during a canal clean-up in Leiden, The Netherlands. We also report the first cases of birds using medical face masks as nesting material, which were also found in the Dutch canals. To place these new findings in context, we collected online reported interactions of animals with PPE litter, since the start of the pandemic. This resulted in the first overview of cases of entanglement, entrapment and ingestion of COVID-19 litter by animals and the use of it as nesting material. We signal COVID-19 litter as a new threat to animal life as the materials designed to keep us safe are actually harming animals around us. To understand the full scale of this problem, we welcome anyone to contribute to our overview by submitting their observations online at www.covidlitter.com. To further prevent PPE litter, it is recommended that, when possible, reusable alternatives are used.

Effects of Laboratory Housing Conditions on Core Temperature and Locomotor Activity in Mice

Drug developers worldwide assess compound safety and efficacy using measures that include mouse core temperature andlocomotor activity. Subtle differences in animal housing conditions between institutions can alter these values, impacting scientific rigor and reproducibility. In these studies, adult male NIH Swiss mice were surgically implanted with radiotelemetry probes that simultaneously monitored core temperature and locomotor activity across various housing conditions. In the first study, ambient temperature was varied between 20 °C and 28 °C in groups of singly housed mice. Additional studies held the mice at a constant ambient temperature and examined the effects of cage density (housing animals singly or in groups of 3 or 6), bedding change and provision of nesting material, and the availability of a running wheel on core temperature and locomotor activity. Mice overwhelmingly maintained species-typical core temperatures across all ambient temperatures,across all housing conditions, when bedding was fresh or old, and with or without the provision of cotton squares as nesting material. However, engaging in wheel running and the combination of fresh bedding and cotton squares transiently increased core temperatures beyond the species-typical range. Similarly, the circadian distribution of locomotor activity was significantly disrupted by placing animals in cages with fresh bedding or nesting material, or by performing both of these manipulations concurrently during the light period. These findings suggest that standard husbandry practices and common housing conditions may transiently affect core temperature in adult mice. Furthermore, these practices may have profound and relatively long-lasting effects on motor activity and the regulation of circadian rhythms.