RESUMO

The study of phenotypic variation within species in response to different environments is a central issue in evolutionary and ecological physiology. Particularly, ambient temperature is one of the most important factors modulating interactions between animals and their environment. Phyllotis xanthopygus, a small Andean rodent, exhibits intraspecific differences along an altitudinal gradient in traits relevant to energy balance that persist after acclimation to common experimental temperatures. Therefore, we aim to explore geographic variations in energetic traits of P. xanthopygus and to assess the contribution of phenotypic plasticity to population differences. We compared metabolic rate and thermal conductance in response to different acclimation temperatures in animals collected at distinct altitudes (F0 generation) and in their offspring, born and raised under common-garden conditions (F1 generation). We found intraspecific differences in resting metabolic rate (RMR) of animals collected at different altitudes that were no longer evident in the F1 generation. Furthermore, although both generations showed the same pattern of RMR flexibility in response to acclimation temperature, its magnitude was lower for the F1 individuals. This suggests that developmental conditions affect the short-term acclimation capacity of this trait during adulthood. On the other hand, thermal conductance (C) showed irreversible plasticity, as animals raised in the laboratory at stable warm conditions had a relatively higher C than the animals from the field, showing no adjustments to thermal acclimation during adulthood in either group. In sum, our results support the hypothesis that the developmental environment shapes energetic traits, emphasizing the relevance of incorporating ontogeny in physiological studies.

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ABSTRACT Growing evidence suggests that parasite-infected prey is more vulnerable to predation. However, the mechanism underlying this phenomenon is obscure. In small mammals, analgesia induced by environmental stressors is a fundamental component of the defensive repertoire, promoting defensive responses. Thus, the reduced analgesia may impair the defensive ability of prey and increase their predation risk. This study aimed to determine whether coccidia infection increases the vulnerability to predation in root voles, Microtus oeconomus (Pallas, 1776), by decreased analgesia. Herein, a predator stimulus and parasitic infection were simulated in the laboratory via a two-level factorial experiment, then, the vole nociceptive responses to an aversive thermal stimulus were evaluated. Further, a field experiment was performed to determine the overwinter survival of voles with different nociceptive responses via repeated live trapping. The coccidia-infected voles demonstrated reduced predator-induced analgesia following exposure to predator odor. Meanwhile, pain-sensitive voles had lower overwinter survival than pain-inhibited voles in enclosed populations throughout the duration of the experiment. Our findings suggest that coccidia infection attenuates predator-induced analgesia, resulting in an increased vulnerability to predation.

Assuntos

RESUMO

ABSTRACT Growing evidence suggests that parasite-infected prey is more vulnerable to predation. However, the mechanism underlying this phenomenon is obscure. In small mammals, analgesia induced by environmental stressors is a fundamental component of the defensive repertoire, promoting defensive responses. Thus, the reduced analgesia may impair the defensive ability of prey and increase their predation risk. This study aimed to determine whether coccidia infection increases the vulnerability to predation in root voles, Microtus oeconomus (Pallas, 1776), by decreased analgesia. Herein, a predator stimulus and parasitic infection were simulated in the laboratory via a two-level factorial experiment, then, the vole nociceptive responses to an aversive thermal stimulus were evaluated. Further, a field experiment was performed to determine the overwinter survival of voles with different nociceptive responses via repeated live trapping. The coccidia-infected voles demonstrated reduced predator-induced analgesia following exposure to predator odor. Meanwhile, pain-sensitive voles had lower overwinter survival than pain-inhibited voles in enclosed populations throughout the duration of the experiment. Our findings suggest that coccidia infection attenuates predator-induced analgesia, resulting in an increased vulnerability to predation.

RESUMO

Growing evidence suggests that parasite-infected prey is more vulnerable to predation. However, the mechanism underlying this phenomenon is obscure. In small mammals, analgesia induced by environmental stressors is a fundamental component of the defensive repertoire, promoting defensive responses. Thus, the reduced analgesia may impair the defensive ability of prey and increase their predation risk. This study aimed to determine whether coccidia infection increases the vulnerability to predation in root voles, Microtus oeconomus (Pallas, 1776), by decreased analgesia. Herein, a predator stimulus and parasitic infection were simulated in the laboratory via a two-level factorial experiment, then, the vole nociceptive responses to an aversive thermal stimulus were evaluated. Further, a field experiment was performed to determine the overwinter survival of voles with different nociceptive responses via repeated live trapping. The coccidia-infected voles demonstrated reduced predator-induced analgesia following exposure to predator odor. Meanwhile, pain-sensitive voles had lower overwinter survival than pain-inhibited voles in enclosed populations throughout the duration of the experiment. Our findings suggest that coccidia infection attenuates predator-induced analgesia, resulting in an increased vulnerability to predation.(AU)

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Leptospira is a bacteria that causes leptospirosis and is transmitted through water, soil, or mud that is contaminated by the urine of infected animals. Although it is mainly associated with the urban environment, Leptospires also circulate in rural and wild environments. This study aimed to investigate the role of small mammals in leptospirosis epidemiology in the western Amazon, Brazil. In total, 103 animals from 23 species belonging to the orders Didelphimorphia and Rodentia were captured. Blood, kidney, and urine samples were collected and Microscopic Agglutination Test (MAT), lipL32 PCR, secY sequencing, and culturing were conducted. MAT was reactive on 1/15 sera, and no bacterial isolate was obtained. PCR yielded 44.7% positive samples from 16 species. Twenty samples were genetically characterized and identified as L. interrogans (n = 12), L. noguchii (n = 4), and L. santarosai (n = 4). No statistical association was found between the prevalence of infection by Leptospira spp. in small mammals within carrier/hosts species, orders, study area, and forest strata. Our results indicate a high prevalence of pathogenic Leptospira spp. in several rodent and marsupial species and report the first evidence of Leptospira spp. carrier/hosts in the Brazilian Western Amazon.

RESUMO

AIM: Incorporate species' trait information together with climate projections for associated habitat to assess the potential vulnerability of rodent taxa to climate change. LOCATION: Oaxaca State, Mexico. METHODS: We used a trait-based approach together with climate exposure models to evaluate the vulnerability of rodent species to projected climate conditions in the study region. Vulnerability was estimated based on three factors: (a) Level of climatic exposure that species are projected to experience across their current statewide range; (b) inherent species-specific sensitivity to stochastic events; and (c) species' capacity to cope with climate change effects. We defined species as inherently sensitive if they had any of the following: restricted geographic distribution in Mexico; narrow altitudinal range; low dispersal ability; or long generation length. RESULTS: Vulnerability varied depending on the climate change scenario applied. Under the MPI general circulation model and current emissions trends, by 2099, all species evaluated were projected to have some level of threat (vulnerable for at least one factor), with 4 out of 55 species vulnerable for all three factors, 29 for two factors, and 22 for one factor. Six out of ten rodent species endemic to Oaxaca were vulnerable for two or more factors. We found that species with narrow and restricted-range distributions combined with low adaptive capacity were projected to be particularly vulnerable. MAIN CONCLUSIONS: By including species-specific trait information in climate exposure assessments, researchers can contextualize and enhance their understanding about how climate change is likely to affect individual taxa in an area of interest. As such, studies like this one provide more relevant threat assessment information than exposure analyses alone and serve as a starting point for considering how climatic changes interact with an array of other variables to affect native species across their range.

RESUMO

Non-volant small mammals, which include small-bodied representatives from several mammal orders, have been used as a model group to test the effects of habitat conversion and edge creation on biodiversity. Small mammals occupy a large variety of habitat types and vegetation strata, and have varied lifestyles and diets. They include species with slow-to fast-life history (the Etruscan shrew Suncus etruscus and European Hare Lepus europaeus, respectively) and with very specialized to very generalist habits and diets (the Atlantic bamboo rat Kannabateomys amblyonyx and house mouse Mus musculus, respectively). There are no databases with global coverage focusing on small mammal composition in natural and human-modified habitats and that include neglected natural habitats (e.g. grasslands and savannas). Here, peer-reviewed articles were searched in the primary literature to synthesize almost half century (1973-2017) of research on small mammal composition in natural forests, grasslands and their natural edges, and in five types of human-modified habitats (human-induced forest edges, human-induced grassland edges, crop fields, clear-cuts and tree plantations). The complete database includes information from 199 peer-reviewed articles. Presence data were obtained for 534 species (including 30 unidentified) in 551 sites distributed in 45 countries, 92 ecoregions, 10 biomes and six realms. Measurements of sampling effort and number of species records (number of individuals, captures) per habitat were also obtained, from which researchers can calculate a measure of abundance standardized by the sampling effort. The database will be useful for researchers interested in local-to broad-scale patterns of alpha- and beta-diversity in natural and human-modified habitats.

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Photosynthetic productivity is a key determinant of the abundance and distribution of biodiversity around the world. The effect of this productivity on the distribution patterns of mammals is frequently invoked; however, it is seldom measured directly. In this study, we used Sherman live traps set in dry and rainy seasons across a 2300-m elevation gradient in southwestern Mexico to assess small rodent species distributions, and to relate these patterns to habitat structure, climate, and a well-accepted measure of photosynthetic productivity: the normalized difference vegetation index (NDVI). While habitat structure and climate helped explain some of the patterns observed, NDVI proved to be the most important contributing variable for most of the distribution models. We also found that partitioning the gradient-distribution model by trapping season revealed strong differences in terms of the effect of NDVI and the other explanatory variables. For example, lower elevations were associated with seasonal and year-round reductions in rodent diversity and were composed almost exclusively of granivore-based species assemblages. By contrast, the middle and upper elevations were more species rich, less affected by seasonality, and characterized by omnivorous species. Our results suggest that the positive productivity-diversity relationship found may be due, at least in part, to increased food resources and niche opportunities at more productive elevations. Increased diversity at the higher elevations may also be partially due to reductions in competition that result from productivity increases, as well as from the broader spectrum of feeding guild representation that it and the lack of seasonality allow.

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The Pantanal is a South American biome characterized by extensive plains and stark environmental seasonality. Several habitats are subject to annual flooding, forcing small mammal species to aggregate in dry forest patches, which most likely influences their population dynamics and life history strategies. In order to investigate the seasonal influence on the life history traits of these small mammals, we conducted a 2-year mark-recapture study in the southeastern region of the Brazilian Pantanal (Nhecolândia) and analyzed the population dynamics of the most abundant small mammal species with the jackknife estimator. A trapping effort of 21,560 trap-nights resulted in 615 individuals in 1,171 captures (success = 5.43%). Three species of rodents - Oecomys mamorae (Thomas, 1906), Thrichomys pachyurus (Wagner, 1845), and Clyomys laticeps (Thomas, 1841) - and three species of marsupials - Gracilinanus agilis (Burmeister, 1854), Thylamys macrurus (Olfers, 1818), and Monodelphis domestica (Wagner, 1842) - were obtained. The most abundant species was O. mamorae, followed by G. agilis and T. pachyurus. Oecomys mamorae was more abundant in the wet season and presented an opportunistic reproductive strategy. Gracilianus agilis displayed increased population sizes in the dry season and synchronized, seasonal reproduction during the rainy season. Thrichomys pachyurus had a small population size, delayed response to variations in environmental conditions and higher reproductive rates in the dry season. All species revealed different life history strategies (seasonal, opportunistic or delayed response to environmental variations), coinciding with periods of higher resource availability in order to maximize survival.

RESUMO

The Pantanal is a South American biome characterized by extensive plains and stark environmental seasonality. Several habitats are subject to annual flooding, forcing small mammal species to aggregate in dry forest patches, which most likely influences their population dynamics and life history strategies. In order to investigate the seasonal influence on the life history traits of these small mammals, we conducted a 2-year mark-recapture study in the southeastern region of the Brazilian Pantanal (Nhecolândia) and analyzed the population dynamics of the most abundant small mammal species with the jackknife estimator. A trapping effort of 21,560 trap-nights resulted in 615 individuals in 1,171 captures (success = 5.43%). Three species of rodents - Oecomys mamorae (Thomas, 1906), Thrichomys pachyurus (Wagner, 1845), and Clyomys laticeps (Thomas, 1841) - and three species of marsupials - Gracilinanus agilis (Burmeister, 1854), Thylamys macrurus (Olfers, 1818), and Monodelphis domestica (Wagner, 1842) - were obtained. The most abundant species was O. mamorae, followed by G. agilis and T. pachyurus. Oecomys mamorae was more abundant in the wet season and presented an opportunistic reproductive strategy. Gracilianus agilis displayed increased population sizes in the dry season and synchronized, seasonal reproduction during the rainy season. Thrichomys pachyurus had a small population size, delayed response to variations in environmental conditions and higher reproductive rates in the dry season. All species revealed different life history strategies (seasonal, opportunistic or delayed response to environmental variations), coinciding with periods of higher resource availability in order to maximize survival.

RESUMO

The Pantanal is a South American biome characterized by extensive plains and stark environmental seasonality. Several habitats are subject to annual flooding, forcing small mammal species to aggregate in dry forest patches, which most likely influences their population dynamics and life history strategies. In order to investigate the seasonal influence on the life history traits of these small mammals, we conducted a 2-year mark-recapture study in the southeastern region of the Brazilian Pantanal (Nhecolândia) and analyzed the population dynamics of the most abundant small mammal species with the jackknife estimator. A trapping effort of 21,560 trap-nights resulted in 615 individuals in 1,171 captures (success = 5.43%). Three species of rodents - Oecomys mamorae (Thomas, 1906), Thrichomys pachyurus (Wagner, 1845), and Clyomys laticeps (Thomas, 1841) - and three species of marsupials - Gracilinanus agilis (Burmeister, 1854), Thylamys macrurus (Olfers, 1818), and Monodelphis domestica (Wagner, 1842) - were obtained. The most abundant species was O. mamorae, followed by G. agilis and T. pachyurus. Oecomys mamorae was more abundant in the wet season and presented an opportunistic reproductive strategy. Gracilianus agilis displayed increased population sizes in the dry season and synchronized, seasonal reproduction during the rainy season. Thrichomys pachyurus had a small population size, delayed response to variations in environmental conditions and higher reproductive rates in the dry season. All species revealed different life history strategies (seasonal, opportunistic or delayed response to environmental variations), coinciding with periods of higher resource availability in order to maximize survival.

RESUMO

I examined the diet of breeding White-tailed Kites (Elanus leucurus; Aves; Accipitridae) and Barn Owls (Tyto alba; Aves; Tytonidae) in an agrarian area of southern Brazil by analyzing regurgitated prey remains. The objective was to evaluate how these raptors, which differ markedly in their hunting activity periods (owls are nocturnal and kites diurnal), share their mammalian food component. 2,087 prey consumed by Barn Owls and 1,276 by White-tailed Kites were identified. They presented a high overlap of food-niches (Piankas index was 0.98). Based on the daily activity period of their main small mammal prey, a lower overlap would be expected. The crepuscular/nocturnal Mus musculus was the main prey for the diet of breeding Barn Owls (81%) and White-tailed Kites (63%). This small exotic rodent provided 63% of the small mammal biomass ingested by owls and 44% by kites. Larger native small mammals were also considered important for the diet of kites, mainly because of their biomass contribution. Although these raptors differ markedly in their hunting activity periods, Barn Owls and White-tailed Kites are very similar predators in southern Brazil, overlapping their diets.

Examinaram-se as dietas do gavião-peneira (Elanus leucurus; Aves; Accipitridae) e da coruja suindara (Tyto alba; Aves; Tytonidae) em atividade reprodutiva numa área agrícola no Sul do Brasil, analisando restos de presas regurgitadas. O objetivo foi avaliar como estes predadores que diferem marcadamente quanto aos seus períodos de atividade de caça (a coruja é noturna e o gavião diurno) partilham seu componente alimentar de pequenos mamíferos. Identificaram-se 2087 presas consumidas pela suindara e 1276 pelo gavião-peneira. Eles apresentaram uma alta sobreposição de seus nichos alimentares (índice de Pianka de 0,98). Com base no período diário de atividade de suas principais presas de pequenos mamíferos, uma sobreposição menor seria esperada. O roedor crepuscular/noturno Mus musculus foi a principal presa para a dieta da suindara (81%) e do gavião-peneira (63%). Este pequeno roedor exótico forneceu 63% da biomassa de pequenos mamíferos ingerida pela coruja e 44% pelo gavião. Espécies maiores de pequenos mamíferos nativos também foram importantes para a dieta do gavião-peneira, principalmente devido às suas contribuições de biomassa. Embora haja diferenças marcantes quanto aos seus períodos de atividade de caça, a suindara e o gavião-peneira são predadores muito semelhantes no Sul do Brasil, sobrepondo amplamente suas dietas.

RESUMO

Since disturbance is an important ecological factor affecting species diversity in natural environments, the increasing human occupation rate in Brazilian Atlantic rainforest, which supports about 50% of Brazil's human population, has resulted in intense habitat degradation and fragmentation. Within this rainforest, animal and plant species have been lost at a high rate, and biological and diversity is presently vulnerable. Various animals community studies along a gradient of environmental disturbances have shown that the highest species diversities occur in habitats with intermediate levels of disturbance frequency and intensity. In the present study, which was carried out in the Atlantic forest of Ilha Grande (23° 11' S and 44° 12' W), an island located on the southern coast of Rio de Janeiro State, southeastern Brazil, we estimated species richness, diversity, and abundance of small mammals in three forest areas having different disturbance levels. This was done, in each of these areas and in an anthropic area that they surround, by establishing trails 200 m long, in which points were marked at 20 m intervals. The work involved a total effort of 4800 trap/nights. We also measured some habitat variables at each site in order to evaluated their disturbance levels. Our data showed that the two most conserved forests had the lower species richness and small mammal diversity, while in the anthropic area wild species were absent. The forest with an intermediary level of disturbance showed higher values for species richness and diversity, with the anthropic area presenting the highest disturbance level.

Os distúrbios são importantes fatores ecológicos afetando a diversidade de espécies em ambientes naturais. Na Floresta Atlântica vive cerca de 50% da população humana do Brasil. A crescente ocupação humana neste ecossistema, resultou em uma intensa degradação e fragmentação do hábitat, tornando vulnerável a sua diversidade biológica e ocasionando uma alta taxa de perda de espécies animais e vegetais. Alguns estudos de comunidades têm demonstrado que ao longo de um gradiente de perturbação ambiental, os maiores valores de diversidade de espécies são encontrados em hábitats com níveis intermediários de frequência e de intensidade de distúrbios. No presente estudo, nós estimamos a riqueza, diversidade e abundância de espécies de pequenos mamíferos em três áreas de Mata Atlântica com diferentes níveis de distúrbio. O estudo foi conduzido na Mata Atlântica da Ilha Grande (23° 11' S e 44° 12' W), uma ilha localizada no Sul do estado do Rio de Janeiro, Sudeste do Brasil. Em cada uma das três áreas de florestas e em uma área antrópica rodeada por estas florestas, nós estabelecemos 10 trilhas paralelas com 200 metros de comprimento (com pontos a cada 20 m de intervalo e pontos adicionais acima do solo), num esforço total de 4800 armadilhas/noite. Nós também medimos algumas variáveis estruturais do hábitat para avaliar o nível de distúrbio em cada área. Nossos dados mostraram que as duas florestas mais conservadas tiveram os mais baixos valores de riqueza e diversidade de espécies e que na área antrópica ocorreu uma perda quase total de espécies silvestres. A floresta com nível intermediário de distúrbio teve os maiores valores de riqueza e diversidade de espécies, considerando a área antrópica como um hábitat sob alto grau de distúrbio.

RESUMO

We studied the ectoparasite and the Amblyopinini beetle fauna associated with four small mammal species of the Atlantic Rainforest of Ilha Grande, an island located off the southern Rio de Janeiro State Coast, Southeastern Brazil, analyzing to what extent the parasites were specific to each region of the host body. During the study, a total of 90 individual rodents were captured: 61 Proechimys iheringi Thomas, 1911 (Echymyidae), 22 Sciurus aestuans (Thomas, 1901) (Sciuridae), 4 Oxymycterus sp. (Waterhouse, 1837), and 2 Nectomys squamipes (Brants, 1827) (Sigmodontinae). The data showed that the ectoparasites and Amblyopinini on some rodent hosts in Ilha Grande tend to prefer particular host body sites, and that some ectoparasite species sites may overlap owing to their inaccessibility to the host.

Estudamos a fauna de ectoparasitos e besouros Amblyopinini associada a quatro espécies de pequenos mamíferos da Mata Atlântica da Ilha Grande, localizada no sul do Estado do Rio de Janeiro, Sudeste do Brasil, analisando em que extensão os ectoparasitos seriam específicos de cada região do corpo do hospedeiro. Durante o estudo capturamos um total de 90 roedores: 61 Proechimys iheringi Thomas, 1911 (Echymyidae), 22 Sciurus aestuans (Thomas, 1901) (Sciuridae), 4 Oxymycterus sp. (Waterhouse, 1837) e 2 Nectomys squamipes (Brants, 1827) (Sigmodontinae). Os dados mostraram que os ectoparasitos e os Amblyopinini encontrados vivendo nos hospedeiros roedores da Ilha Grande apresentam preferência por algumas áreas específicas do corpo do hospedeiro. Contudo, algumas espécies de ectoparasitos podem se sobrepor em alguns sítios que utilizam, aparentemente devido à limitação de acesso a esses sítios pelos hospedeiros, reduzindo sua remoção e aumentando a chance de que ali ocorram.

RESUMO

We studied the ectoparasite and the Amblyopinini beetle fauna associated with four small mammal species of the Atlantic Rainforest of Ilha Grande, an island located off the southern Rio de Janeiro State Coast, Southeastern Brazil, analyzing to what extent the parasites were specific to each region of the host body. During the study, a total of 90 individual rodents were captured: 61 Proechimys iheringi Thomas, 1911 (Echymyidae), 22 Sciurus aestuans (Thomas, 1901) (Sciuridae), 4 Oxymycterus sp. (Waterhouse, 1837), and 2 Nectomys squamipes (Brants, 1827) (Sigmodontinae). The data showed that the ectoparasites and Amblyopinini on some rodent hosts in Ilha Grande tend to prefer particular host body sites, and that some ectoparasite species sites may overlap owing to their inaccessibility to the host.

Estudamos a fauna de ectoparasitos e besouros Amblyopinini associada a quatro espécies de pequenos mamíferos da Mata Atlântica da Ilha Grande, localizada no sul do Estado do Rio de Janeiro, Sudeste do Brasil, analisando em que extensão os ectoparasitos seriam específicos de cada região do corpo do hospedeiro. Durante o estudo capturamos um total de 90 roedores: 61 Proechimys iheringi Thomas, 1911 (Echymyidae), 22 Sciurus aestuans (Thomas, 1901) (Sciuridae), 4 Oxymycterus sp. (Waterhouse, 1837) e 2 Nectomys squamipes (Brants, 1827) (Sigmodontinae). Os dados mostraram que os ectoparasitos e os Amblyopinini encontrados vivendo nos hospedeiros roedores da Ilha Grande apresentam preferência por algumas áreas específicas do corpo do hospedeiro. Contudo, algumas espécies de ectoparasitos podem se sobrepor em alguns sítios que utilizam, aparentemente devido à limitação de acesso a esses sítios pelos hospedeiros, reduzindo sua remoção e aumentando a chance de que ali ocorram.