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1. Habitat use and seed removal by invasive rats ( Rattus rattus ) in disturbed and undisturbed rain forest, Puerto Rico

   https://doi.org/10.1111/btp.12640  

   Shiels, Aaron B.; Ramírez de Arellano, Gabriela E. (March 2019, Biotropica)

   Abstract Despite frequent occurrences of invasive rats (Rattusspp.) on islands, their known effects on forests are limited. Where invasive rats have been studied, they generally have significant negative impacts on native plants, birds, and other animals. This study aimed to determine invasive rat distribution and effects on native plant populations via short‐term seed removal trials in tropical rain forest habitats in the Luquillo Experimental Forest, Puerto Rico. To address the first objective, we used tracking tunnels (inked and baited cards inside tunnels enabling animal visitors’ footprints to be identified) placed on the ground and in the lower canopy within disturbed (treefall gaps, hurricane plots, stream edges) and undisturbed (continuous forest) habitats. We found that rats are present in all habitats tested. Secondly, we compared seed removal of four native tree species (Guarea guidonia,Buchenavia capitata, Tetragastris balsamifera,andPrestoea acuminata) between vertebrate‐excluded and free‐access treatments in the same disturbed and undisturbed habitats. Trail cameras were used to identify animals responsible for seed contact and removal. Black rats (Rattus rattus) were responsible for 65.1% of the interactions with seeds, of which 28.6% were confirmed seed removals. Two plant species had significantly more seeds removed in disturbed (gaps) than undisturbed forest.Prestoea acuminatahad the lowest seed removal (9% in 10 days), whereas all other species had >30% removal. Black rats are likely influencing fates of seeds on the forest floor, and possibly forest community composition, through dispersal or predation. Further understanding of rat–plant interactions may be useful for formulating conservation strategies. 

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2. “I don’t feel safe sitting in my own yard”: Chicago resident experiences with urban rats during a COVID-19 stay-at-home order

   https://doi.org/10.1186/s12889-021-11095-y  

   Murray, Maureen H.; Byers, Kaylee A.; Buckley, Jacqueline; Magle, Seth B.; Maffei, Dorothy; Waite, Preeya; German, Danielle (December 2021, BMC Public Health)

   null (Ed.)

   Abstract Background Encounters with rats in urban areas increase risk of human exposure to rat-associated zoonotic pathogens and act as a stressor associated with psychological distress. The frequency and nature of human-rat encounters may be altered by social distancing policies to mitigate the COVID-19 pandemic. For example, restaurant closures may reduce food availability for rats and promote rat activity in nearby residential areas, thus increasing public health risks during a period of public health crisis. In this study, we aimed to identify factors associated with increased perceived exposure to rats during a stay-at-home order, describe residents’ encounters with rats relevant to their health and well-being, and identify factors associated with increased use of rodent control. Methods Urban residents in Chicago, a large city with growing concerns about rats and health disparities, completed an online questionnaire including fixed response and open-ended questions during the spring 2020 stay-at-home order. Analyses included ordinal multivariate regression, spatial analysis, and thematic analysis for open-ended responses. Results Overall, 21% of respondents ( n  = 835) reported an increase in rat sightings around their homes during the stay-at-home order and increased rat sightings was positively associated with proximity to restaurants, low-rise apartment buildings, and rat feces in the home ( p  ≤ 0.01). Many respondents described feeling unsafe using their patio or yard, and afraid of rats entering their home or spreading disease. Greater engagement with rodent control was associated with property ownership, information about rat control, and areas with lower incomes ( p  ≤ 0.01). Conclusions More frequent rat encounters may be an unanticipated public health concern during periods of social distancing, especially in restaurant-dense areas or in low-rise apartment buildings. Rat presence may also limit residents’ ability to enjoy nearby outdoor spaces, which otherwise might buffer stress experienced during a stay-at-home order. Proactive rat control may be needed to mitigate rat-associated health risks during future stay-at-home orders. 

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3. Microbial diversity in active and abandoned desert kangaroo rat burrows and from proximal surface sand

   https://doi.org/10.1128/spectrum.01388-24  

   Aydin, Duygu; Parks, Janice M; Tirkes, Sera; Collins, Clint E; Akin, Idil Deniz; Friesen, Maren L; Call, Douglas R; Beyenal, Haluk (May 2025, Microbiology Spectrum)

   ABSTRACT Desert kangaroo rats (Dipodomys deserti) construct burrows that can create micro-niches favorable to increased microbial activity. The aim of this study was to characterize the bacterial communities found in kangaroo rat burrows, in proximal desert surface sand, and in samples from kangaroo rats. We collected samples from burrow ceilings of actively inhabited burrows, from burrows that were no longer in use, and from the proximal surface sand in the Sonoran Desert, Yuma, AZ. Following DNA extraction from samples, 16S rRNA gene sequencing was performed, and functional predictions were made and assessed for each characterized bacterial community. Active burrow samples exhibited greater alpha diversity but similar beta diversity when compared to surface sand (P< 0.05), with no significant differences observed between abandoned and active burrows. Bacterial genera and genes related to nitrogen fixation, nitrification, and urea hydrolysis were found in significantly higher abundance in active burrows compared to the surface sand (P< 0.05). The core microbiome of active burrow samples was different from surface sand, including higher abundances ofAcidimicrobialesandAcidobacteriasubdivision Gp7. Active burrow samples included 30 unique genera. Kangaroo rat anal swabs shared 12, cheek pouches shared 6 unique genera with burrows. These findings suggest that kangaroo rats can shape the microbial composition of their burrow environment through the introduction of food material and waste, facilitating increased species richness and bacterial diversity.IMPORTANCEAnimals can alter soil parameters, including microbial composition through burrowing activities, excretion, and dietary composition. Desert kangaroo rats (Dipodomys deserti) construct burrows within loose desert sand that have microclimatic conditions different from the surrounding desert climate. In this study, we explored the effect of disturbance from kangaroo rat activities on the bacterial composition of sand. We compared the bacterial community compositions of kangaroo rat (D. deserti) samples, their burrows, and the proximal surface sand. The results showed that burrow sand shows higher richness and diversity of bacterial community with higher abundances of bacterial genera and genes associated with nitrogen fixation, nitrification, and urea hydrolysis compared to the surface sand. These findings suggest that kangaroo rats affect the microbial composition of their burrow environment through the introduction of food material and waste. 

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4. Multiple paths toward repeated phenotypic evolution in the spiny‐leg adaptive radiation ( Tetragnatha ; Hawai'i)

   https://doi.org/10.1111/mec.17082  

   Cerca, José; Cotoras, Darko_D; Santander, Cindy_G; Bieker, Vanessa_C; Hutchins, Leke; Morin‐Lagos, Jaime; Prada, Carlos_F; Kennedy, Susan; Krehenwinkel, Henrik; Rominger, Andrew_J; et al (July 2023, Molecular Ecology)

   Abstract The repeated evolution of phenotypes provides clear evidence for the role of natural selection in driving evolutionary change. However, the evolutionary origin of repeated phenotypes can be difficult to disentangle as it can arise from a combination of factors such as gene flow, shared ancestral polymorphisms or mutation. Here, we investigate the presence of these evolutionary processes in the Hawaiian spiny‐legTetragnathaadaptive radiation, which includes four microhabitat‐specialists or ecomorphs, with different body pigmentation and size (Green, Large Brown, Maroon, and Small Brown). We investigated the evolutionary history of this radiation using 76 newly generated low‐coverage, whole‐genome resequenced samples, along with phylogenetic and population genomic tools. Considering the Green ecomorph as the ancestral state, our results suggest that the Green ecomorph likely re‐evolved once, the Large Brown and Maroon ecomorphs evolved twice and the Small Brown evolved three times. We found that the evolution of the Maroon and Small Brown ecomorphs likely involved ancestral hybridization events, while the Green and Large Brown ecomorphs likely evolved through novel mutations, despite a high rate of incomplete lineage sorting in the dataset. Our findings demonstrate that the repeated evolution of ecomorphs in the Hawaiian spiny‐legTetragnathais influenced by multiple evolutionary processes. 

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5. Invasive rodent responses to experimental and natural hurricanes with implications for global climate change

   https://doi.org/10.1002/ecs2.4307  

   Shiels, Aaron B.; Ramírez de Arellano, Gabriela E.; Shiels, Laura (December 2022, Ecosphere)

   Abstract Hurricanes cause dramatic changes to forests by opening the canopy and depositing debris onto the forest floor. How invasive rodent populations respond to hurricanes is not well understood, but shifts in rodent abundance and foraging may result from scarce fruit and seed resources that follow hurricanes. We conducted studies in a wet tropical forest in Puerto Rico to better understand how experimental (canopy trimming experiment) and natural (Hurricane Maria) hurricane effects alter populations of invasive rodents (Rattus rattus[rats] andMus musculus[mice]) and their foraging behaviors. To monitor rodent populations, we used tracking tunnels (inked and baited cards inside tunnels enabling identification of animal visitors' footprints) within experimental hurricane plots (arborist trimmed in 2014) and reference plots (closed canopy forest). To assess shifts in rodent foraging, we compared seed removal of two tree species (Guarea guidoniaandPrestoea acuminata) between vertebrate‐excluded and free‐access treatments in the same experimental and reference plots, and did so 3 months before and 9 months after Hurricane Maria (2017). Trail cameras were used to identify animals responsible for seed removal. Rat incidences generated from tracking tunnel surveys indicated that rat populations were not significantly affected by experimental or natural hurricanes. Before Hurricane Maria there were no mice in the forest interior, yet mice were present in forest plots closest to the road after the hurricane, and their forest invasion coincided with increased grass cover resulting from open forest canopy. Seed removal ofGuareaandPrestoeaacross all plots was rat dominated (75%–100% rat‐removed) and was significantly less after than before Hurricane Maria. However, following Hurricane Maria, the experimental hurricane treatment plots of 2014 had 3.6 times greater seed removal by invasive rats than did the reference plots, which may have resulted from rats selecting post‐hurricane forest patches with greater understory cover for foraging. Invasive rodents are resistant to hurricane disturbance in this forest. Predictions of increased hurricane frequency from expected climate change should result in forest with more frequent periods of grassy understories and mouse presence, as well as with heightened rat foraging for fruit and seed in preexisting areas of disturbance. 

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