Activity Patterns Of Species Research Articles

Activity pattern of Tityus serrulatus (Scorpiones: Buthidae) in an urban area in the state of São Paulo, Brazil.

Tityus serrulatus Lutz & Mello (Scorpiones: Buthidae) is a scorpion endemic to Brazil adapted to synanthropic life, colonising and proliferating in the most populous urban areas in the country. Here, we evaluated its activity pattern in an urban cemetery in the municipality of Americana, state of São Paulo, Brazil. Additionally, we tested the effects of species reproduction and climatic seasons on the activity pattern. The Saudade Municipal Cemetery was sampled between 17:00 and 22:00 h during 455 nights from April 2006 to December 2013. The circular mean and the peak of activity were quantified for the total number of specimens, and for specimens with and without broods. Activity patterns were inferred using a rosette diagram. Circular analysis of variance was used to investigate if activity patterns changed across climatic seasons (wet and dry seasons). A total of 25,969 records (467 specimens with broods) were obtained in the field. The circular mean varied between 19:44 and 19:48 h, and the peak of activity occurred between 18:00 and 20:00 h for all groups. Peaks of activity differed from that recorded under laboratory conditions (between 21:00 and 23:00 h). Activity patterns did not differ for specimens with broods, suggesting that the reproductive condition does not alter the species activity pattern. The activity pattern differed between wet and dry seasons for all specimens and specimens without broods, but differences were small and probably biologically irrelevant, probably because the species tolerates a wide variation in abiotic conditions. Deepening the knowledge of the behaviour activity of T. serrulatus can have practical applications for health surveillance agencies, aiming to increase the effectiveness of scorpion control in urban areas.

Thermal balance in Andean lizards: A perspective from the high mountains

AbstractHigh Andean lizards in the Andes face numerous challenges in high‐altitude environments characterized by significant temperature, spatial and temporal variations. These factors greatly influence their thermal characteristics and adaptive strategies for coping with temperature fluctuations. This study aims were to investigate the thermal biology of high mountain lizards (>2000 m) inhabiting the Andes Mountain range, using information from existing literature, and to identify the potential impacts of the original climate change scenarios developed in this study. Within the Andes, high‐altitude species are primarily found in families like Liolaemidae, Gymnophthalmidae, Tropiduridae, Anolidae and Leiourisauridae. Notably, we found in the literature that the higher body temperatures and maximum critical temperatures in southern species compared to those closer to the tropics. Typically, diurnal and seasonal temperature variations have a significant impact on the body temperature of these high‐altitude lizards, but their adaptive behaviours and physiological mechanisms enhance their resistance to extreme temperatures. Populations situated below the equator often exhibit higher body temperatures and maximum critical temperatures, largely due to their exposure to higher ambient temperatures during summer. With all global warming scenarios indicating temperature increases in latitudinal regions, tropical high‐altitude lizards, historically less thermally adaptable, may be particularly susceptible to these temperature rises. It is crucial to consider that additional factors, such as species activity patterns, thermal resource availability and diminishing suitable thermal habitats, will also play a pivotal role in shaping the future of these lizard species, making the situation even more complex and challenging.

Seasonal variation in the activity pattern of red squirrels and their mammalian predators

Camera traps are a powerful tool to monitor the activity pattern of species over long time periods. Camera data can be used to analyze activity patterns of or temporal niche partitioning among species. Temporal niche partitioning plays an important role for species coexistence and is under constant evolutionary pressure from predator-prey relationships. Our study aimed to investigate temporal shifts in activity patterns of red squirrels and two mammalian predators, red fox and marten (Martes spec.). Previous studies yielded different activity patterns for these species depending on location, season, predator-prey interactions, and food- availability. We used camera traps to monitor the activity of squirrels, red fox and martens throughout a whole year in a mountainous forest in southwestern Germany. We also investigated a possible difference in activity among different color morphs as coloration in mammals is often associated with concealment, for squirrels, however, such an effect could not be demonstrated so far. We found a diurnal activity for squirrels in all seasons with a bimodal activity pattern during spring, trimodal in summer and unimodal in fall and winter. Activity patterns did not differ between black and red color morphs. The activity of the squirrels showed only low to moderate overlaps with fox and marten, but there was still slight variation among seasons. Activity overlaps were higher in spring and summer, which coincides with breeding season. Our results suggest that predators might adjust their activity during squirrel breeding season to increase the chance of preying on their offspring. Squirrels in turn could benefit by minimizing the activity overlap during wintertime when they are highly visible to predators as trees are leaf-free or even snow might enhance the contrast between them and their background. Lastly, our results indicate that temporal niche portioning among red squirrel, red fox and martens might be rather fine scaled.

Year-round vocal activity of two African barbet species

ABSTRACT Passive acoustic monitoring is a reliable method to study species behaviour and ecology, enabling the discovery of species activity patterns, especially in remote locations. Here, we conducted a year-long recording study to describe annual and circadian patterns in the vocal activity of two African barbet species, the Yellow-rumped Tinkerbird Pogoniulus bilineatus and the Western Tinkerbird Pogoniulus coryphaea. We used automated software to detect vocalisations of the two species from 4893 one-hour recordings taken in Cameroon. In total, we obtained 31,526 vocalisations of Yellow-rumped Tinkerbirds and 1318 vocalisations of Western Tinkerbirds. We used generalised additive mixed models to determine whether the month or hour of recording or meteorological conditions influenced the species’ vocal activity. Our results indicated that both tinkerbirds are likely seasonal breeders, as the highest vocal activity of both species was during the dry season. Both species exhibited smaller activity peaks in the wet season. Our study provides new information on the vocal activity patterns of two barbet species, which could be valuable in future monitoring and surveying efforts. This study provides an illustrative example of two useful technologies that facilitate studies in remote areas: passive acoustic monitoring for determining species’ activity patterns and automatic recognition software for the rapid analysis of large datasets.

Activity patterns of the marsh deer: Effects of proxies of human movement, cattle presence, and moon phases on its behavior

AbstractActivity is an important aspect of animal behavior. Intrinsic and extrinsic factors can shape species activity patterns, which can alter and reshape several ecological aspects of the species. Human disturbance is known to modify the activity patterns of various species. The Marsh deer (Blastocerus dichotomus) is the largest Neotropical cervid, and has its southernmost distribution located in the wetlands of the lower Delta of the Paraná river, an area characterized by forestry plantations. We studied how the activity patterns of the marsh deer are affected by proxies of human movement, cattle presence, and moon phases in Argentina. We found that marsh deer presented activity peaks during crepuscular hours and moderate levels of activity during the entire night period. The majority of the independent camera‐trapping events of marsh deer occurred during the first quarter and last quarter phases, and the species was more active on sites far from rivers, which could infer an avoidance of human disturbances. In order to comprehend more deeply the variable effects on the activity patterns of marsh deer in this area, further analyses are needed, particularly using movement data of marked individuals.

Long‐term patterns in ecosystem phenology near Palmer Station, Antarctica, from the perspective of the Adélie penguin

AbstractClimate change is leading to phenological shifts across a wide range of species globally. Polar oceans are hotspots of rapid climate change where sea ice dynamics structure ecosystems and organismal life cycles are attuned to ice seasonality. To anticipate climate change impacts on populations and ecosystem services, it is critical to understand ecosystem phenology to determine species activity patterns, optimal environmental windows for processes like reproduction, and the ramifications of ecological mismatches. Since 1991, the Palmer Antarctica Long‐Term Ecological Research (LTER) program has monitored seasonal dynamics near Palmer Station. Here, we review the species that occupy this region as year‐round residents, seasonal breeders, or periodic visitors. We show that sea ice retreat and increasing photoperiod in the spring trigger a sequence of events from mid‐November to mid‐February, including Adélie penguin clutch initiation, snow melt, calm conditions (low winds and warm air/sea temperature), phytoplankton blooms, shallow mixed layer depths, particulate organic carbon flux, peak humpback whale abundances, nutrient drawdown, and bacterial accumulation. Subsequently, from May to June, snow accumulates, zooplankton indicator species appear, and sea ice advances. The standard deviation in the timing of most events ranged from ~20 to 45 days, which was striking compared with Adélie penguin clutch initiation that varied <1 week. In general, during late sea ice retreat years, events happened later (~5 to >30 days) than mean dates and the variability in timing was low (<20%) compared with early ice retreat years. Statistical models showed the timing of some events were informative predictors (but not sole drivers) of other events. From an Adélie penguin perspective, earlier sea ice retreat and shifts in the timing of suitable conditions or prey characteristics could lead to mismatches, or asynchronies, that ultimately influence chick survival via their mass at fledging. However, more work is needed to understand how phenological shifts affect chick thermoregulatory costs and the abundance, availability, and energy content of key prey species, which support chick growth and survival. While we did not detect many long‐term phenological trends, we expect that when sea ice trends become significant within our LTER time series, phenological trends and negative effects from ecological mismatches will follow.

Biological invasions disrupt activity patterns of native wildlife: An example from wild pigs

Activity patterns are an important behavioral trait linked to animal interactions within food webs. Biological invasions can have impacts on the behavior of native species through predation and competition, but few studies have determined if invasions lead to shifts in activity patterns of native species. Wild pigs (Sus scrofa) are a generalist, invasive vertebrate in North America that may affect activity patterns of native species through competition and predation. We hypothesized native species' activity patterns would differ from their expected activity pattern (i.e., typical hours of daily activity) and be more variable across sites occupied by wild pigs. We used a U.S. nationwide and a regional camera trapping dataset to determine if wild pig presence affected activity patterns of a nocturnal, diurnal, and crepuscular species: northern raccoon (Procyon lotor), eastern gray squirrel (Sciurus carolinensis), and white-tailed deer (Odocoileus virginianus), respectively. We simulated expected activity patterns of each species and overlapped them with observed activity patterns of respective species in populations where wild pigs were present and where they were not detected. Overlap coefficients were used in generalized linear mixed models to determine if wild pig presence explained deviations from the expected activity pattern. When wild pigs were detected, raccoons remained nocturnal, but their activity patterns were less variable, squirrel activity on the ground was less diurnal and their activity patterns were more variable, and deer activity patterns remained similar in both respects. These results highlight how biological invasions may differentially influence native species activity patterns, potentially altering food web-level interactions.

Diversity and vertical distribution patterns of wildlife in Tianzhushan, Shaanxi Province, China.

Biodiversity monitoring is an important means by which to evaluate management effectiveness and develop sound conservation plans. In this study, 52 cameras were installed in the study area of Tianzhushan to assess wildlife diversity and elevational patterns from 2018 to 2019. In total, 9 541 independent photos were collected within 26 565 camera-days. We analysed the relative abundance index (RAI), activity patterns and seasonal activity rhythms of the five most abundant species at 200-m elevational intervals throughout the study area (elevation range 1 400–2 000 m a.s.l.). Based on RAI results, the activity patterns of the five most abundant species (i.e. Susscrofa, Naemorhedusgriseus, Muntiacusreevesi, Arctonyxcollaris and Capricornismilneedwardsii) were analysed. Amongst the detected wild mammals, Susscrofa had the highest RAI value of 9.91, while the occurrence of Tamiopsswinhoei had the lowest RAI at 0.004. In addition, there were significant differences in species activity during the daytime and night-time. RAI of the ungulate community peaked at the 1 600–1 800 m a.s.l. elevational range, thus showing a mid-elevational peak pattern. Differences in vertical distribution patterns were detected for the five most abundant species. Mainland serows and wild boars preferred mid-elevation habitats (1 600–1 800 m a.s.l.), long-tailed gorals preferred mid- and high altitudes (1 600–2 000 m a.s.l.) elevation habitats and Chinese muntjacs and hog badgers preferred low elevation habitats (1 400–1 600 m a.s.l.). Taken together, this is the first study to reveal the five dominant species activity patterns in Tianzhushan, which is of importance for wildlife conservation.

Living with the enemy: activity rhythms of the red fox and some potential preys in an urban environment

The present study aimed at investigating the activity rhythms of the red fox Vulpes vulpes and three potential preys (i.e. the European hedgehog Erinaceus europaeus, the wood mouse Apodemus sylvaticus, and the Norway rat Rattus norvegicus) in an urban environment. Data were collected as a part of a camera trapping survey, carried out within the municipality of Padua (northeastern Italy). In order to analyse species activity patterns, the R overlap package was used and then the Watson-Wheeler test was run to evaluate whether two overlaps were significantly different. Results show that all the investigated species have nocturnal activities, with “moderate” temporal activity overlap between the red fox and its potential prey. The Watson-Wheeler test showed that the hedgehog was the only potential prey that did not show significant differences in the hours of activity compared to those of the red fox. Instead, statistically significant differences were recorded when the activity rhythm of the red fox was compared with that of the wood mouse or the Norway rat. This may indicate the development of antipredator behaviour or the possibility that the red fox is seeking anthropogenic food sources instead of wild prey or, alternatively, other preferred food items.

Distribution, ecology, and conservation of Philochortus zolii in Mauritania: implications for the long-term persistence of an endangered lizard

ABSTRACT Philochortus zolii is a globally endangered lizard known only from five localities scattered across North Africa. The population is thought to be decreasing, but there are almost no data about this Sahara-Sahel endemic lizard. Recently, a sixth population was found in Mauritania, at the coastal peripheral zone of the Diawling National Park, which constitutes a remarkable opportunity to gather ecological information for the first time and to plan conservation actions. Here we assess the P. zolii regional distribution in Mauritania, estimate population abundance, analyse the species activity patterns, characterise the occupied habitats, assess local threats, evaluate the national conservation status, and define an action plan for the local conservation of the species. P. zolii is locally rare and exhibits a much-localised distribution, but additional sampling is needed in other humid areas to fill out the knowledge gap on global distribution. The activity period is very restricted, limited to the central hours of the day, with low detectability and high specialisation in habitat use. The species is evaluated as Critically Endangered at the national level and is threatened by industrial and agriculture developments. These activities have degraded the suitable available habitats and hamper any dispersal possibility. Extreme climatic events related with sea-level rise could decimate the entire Mauritanian population. Any pet trade that may be stimulated by the current discovery should be carefully supervised and monitored. The discovery of this isolated population justifies that coastal habitats should be designated as integral protection zone and included inside the Diawling National Park.

Diversity and activity patterns of medium- and large-sized terrestrial mammals at the Los Tuxtlas Biosphere Reserve, México

Studies on diversity of animal communities allow determination of their species richness and composition. This information is particularly relevant to establish sound conservation programs in biosphere reserves, where human activities should be focused on the sustainable use of natural resources and ensure biodiversity protection. This study estimated the diversity and species richness and determined the species composition and activity patterns of medium- and large-sized terrestrial mammals in the Los Tuxtlas Biosphere Reserve (LTBR) located in Veracruz, Mexico. We set 18 camera traps to record medium and large-sized terrestrial mammals from August 2016 to January 2017. We calculated the trapping rate, guilds, and activity patterns of species. Diversity was estimated with Hill numbers. We compared our estimates with other studies in tropical forest in Mexico. We obtained 308 independent captures of 13 species; Cuniculus paca and Dasyprocta mexicana were the species with the highest trapping rate. Order-0, order-1, and order-2 diversity values were 13.99, 6.50, and 4.75 effective species, respectively, which ranks LTBR the fourth-most diverse reserve of medium- and large-sized terrestrial mammals compared to six other tropical rainforest sites in southern Mexico. We recorded mammals representing five trophic guilds, of which frugivore-folivores (five species) and omnivores (three species) ranked highest. All recorded species were primarily nocturnal (six species) or diurnal (six species). Tamandua mexicana, Leopardus pardalis, L. wiedii, and Eira barbara are listed as endangered in the Mexican Official Standard Norm NOM-059-2019, and L. wiedii is listed as near threatened in the IUCN Red List of Threatened Species. We were able to record 40.6 % of the terrestrial mammal species known to inhabit the LTBR. The absence of large-sized species such as large predators and herbivores was notable. Comparison of medium and large-sized mammal diversity of camera trapping studies in Mexico show that landscape degradation is impoverishing terrestrial mammal communities.

Effect of anthropogenic activity on mammal activity patterns in two ecosystems

Abstract Adaptations in species activity patterns allow animals to avoid risks generated by human activities and domestic and feral species. We aimed to evaluate the effect of anthropogenic activity on mammal activity patterns in two tropical ecosystems -semi-evergreen forest and cloud forest-, and its temporal variation in the Sierra Norte of Oaxaca, Mexico. We expected mammal activity patterns to show significant differences from activity patterns of humans and domestic species. From July 2014 to June 2015, we placed camera traps in 23 sites in a semi-evergreen forest and 23 sites in a cloud forest. We estimated the activity level of each species and calculated the activity overlap between wild species and humans and domestic species in each season. We recorded a total of 16 species of wild mammals, four domestic species, and obtained 738 human records. We found no evidence of an effect of anthropogenic activity on the activity patterns of wild mammals: we found similar activity levels between seasons and ecosystems, and moderate to high overlap between the activity patterns of some wild mammal species and of humans and domestic species. Low human population density, human activity temporal dynamics, and the plasticity of wild species could explain the results of our study.

DON'T SPEED UP, SPEED KILLS: MAMMAL ROADKILLS ON HIGHWAY SECTIONS OF PR-445 IN THE SOUTH OF BRAZIL

Animal-vehicle collisions are the main negative impact of roads on wildlife, where they cause population declines, shifts in community structure, and potential changes in species behavior. Here, we determined mammal roadkill rates and the hotspots with higher rates for medium- and large-bodied mammals on the Highway PR-445 in the state of Paraná, Brazil. We have also evaluated possible differences in the frequency of roadkills concerning species activity patterns and their feeding habits. In doing so, we monitored the PR-445 twice a week between the kilometers 1 and 76, from March 2018 to March 2019, totaling 7296 km after 96 trips. We have recorded 93 mammal roadkills belonging to 17 species, representing a rate of 0.013 individual/km/day. The Carnivora, Didelphimorphia, and Cingulata orders showed to be the most common representatives among the roadkills. Omnivores were more prone to get hit by vehicles than herbivores and carnivores. The type of mammal activity pattern was not determinant in explaining the differences in roadkill rates. Highways in Paraná are among the roads that register the highest number of vehicle collisions with vertebrates in the country. This issue, together with extensive habitat loss and fragmentation, increases the threats to the relictual fauna. Our results indicate that the regions with the highest incidence of mammal roadkills on PR-445 are those close to stretches over rivers and with remnants of native vegetation. Thus, we emphasize that more comprehensive measures (e.g., wildlife passages and speed reducers) are essential to mitigate the impact of roads on wildlife.

A sparse observation model to quantify species distributions and their overlap in space and time

Camera traps and acoustic recording devices are essential tools to quantify the distribution, abundance and behavior of mobile species. Varying detection probabilities among device locations must be accounted for when analyzing such data, which is generally done using occupancy models. We introduce a Bayesian time‐dependent observation model for camera trap data (Tomcat), suited to estimate relative event densities in space and time. Tomcat allows to learn about the environmental requirements and daily activity patterns of species while accounting for imperfect detection. It further implements a sparse model that deals well will a large number of potentially highly correlated environmental variables. By integrating both spatial and temporal information, we extend the notation of overlap coefficient between species to time and space to study niche partitioning. We illustrate the power of Tomcat through an application to camera trap data of eight sympatrically occurring duikerCephalophinaespecies in the savanna – rainforest ecotone in the Central African Republic and show that most species pairs show little overlap. Exceptions are those for which one species is very rare, likely as a result of direct competition.

Bird activity patterns in the understorey of an evergreen forest in Oaxaca, Mexico

Activity patterns of species are related to their physiology, their behaviour and the environment and can change in response to different factors, such as interactions between species. Bird species, typical of the understorey, show morphological and ecological similarities and must thus have some mechanism of ecological separation, such as temporal niche partitioning. The objective of this study was to provide information about activity patterns and activity overlap of bird species typical of the understorey. We expected temporal niche partitioning between ecologically-similar species. We placed camera traps in 29 sampling points in a high evergreen forest in the southeast of Mexico between 2011 and 2013. All species were mainly diurnal and, contrary to what we expected, there was temporal partitioning between tinamids, but not in galliforms and columbiforms. The degree of activity overlap might reflect a solitary or group lifestyle of the three sets of species, as well as shared behavioural preferences and similar adaptations. These results contribute to our knowledge of the basic biology and behavioural ecology of birds of the understorey.

Activity patterns of jaguar and puma and their main prey in the Greater Madidi-Tambopata Landscape (Bolivia, Peru)

Abstract Activity pattern studies can help explain the coexistence of competing species. Between 2001 and 2017 we evaluated the activity pattern overlap of jaguar (Panthera onca), puma (Puma concolor), and their main prey, using camera traps at 17 Amazonian sites in the Greater Madidi-Tambopata Landscape. We used the Kernel density estimation to generate species activity patterns and the overlap between both cats. We then calculated the overlap coefficient (Δ) by carrying out 10,000 bootstraps (95%). Both cats were active 24 h a day. The puma has higher nocturnal activity (57%), whilst jaguar activity is split almost equally between night (53%) and day (47%). We did not find temporal segregation between jaguars and pumas, which showed similar activity patterns with a high overlapping coefficient (Δ4 = 0.84; 0.78–0.91). Also, we did not find significant differences between Male and Female activity patterns for both species (X2 = 0.50, gl = 1, P = 0.47). Moreover, both cats had significant overlap with the activity patterns of their main prey. Temporal segregation was not detected in any of our study sites within the Greater Madidi-Tambopata Landscape, suggesting that in this region, these predators employ other mechanisms to avoid competition.

Foraging Ecology of the Leaf-Cutter Ant, Acromyrmex subterraneus (Hymenoptera: Formicidae), in a Neotropical Cerrado Savanna

Fungus-farming ants cultivate a fungal symbiont inside the nest that serves as a food source. Leaf-cutter ants are distinctive among fungus-farmers because they forage for fresh plant material to nurture the fungus. Here we investigate the foraging ecology of Acromyrmex subterraneus (Forel) in the Brazilian cerrado savanna. We examined the species activity pattern, forage material collected, and the relationship between load mass and forager size. Ant activity peaked at night and was negatively related to temperature but positively related to relative air humidity. The majority of the items collected by ants was plant material: dry and fresh leaves, flowers, and fruits. Trunk trails ranged from 0.7 to 13 m and colony home ranged from 2 to 28 m2, indicating that ants collect material nearby the nest. Total load mass was positively associated with forager size, especially in the case of leaves. The negative relationship between ant size and burden suggests that ants might optimize their delivery rate by collecting lighter substrates more frequently. Given their pest status, most studies on leaf-cutters are undertaken in human-altered environments. Information on A. subterraneus in native cerrado is imperative given the threatened status of this vegetation. Leaf-cutters thrive in disturbed cerrado and severe seedling herbivory may hinder vegetation recovery. Our fieldwork may provide insights for management techniques of Acromyrmex colonies in agroecosystems, as well as for restoration programs of degraded cerrado areas.

Patrones de actividad de la chachalaca pálida (Ortalis poliocephala)

Los patrones de actividad de las poblaciones animales fluctúan a lo largo del año, como respuesta a la disponibilidad de recursos, cambios en el clima y actividad de depredadores. Estudiar los patrones de actividad de las especies es necesario no sólo para aumentar el conocimiento de su historia natural sino también para la planeación de muestreos acordes a los periodos de mayor actividad. Con la finalidad de reconocer los patrones de actividad de la chachalaca pálida (Ortalis poliocephala) en una selva seca del suroeste de México en dos temporadas, usamos la información recabada con cámaras-trampa durante los inviernos de 2011-2012 y 2012-2013 y las primaveras de 2012 y 2013. La actividad diaria de la chachalaca pálida fue bimodal con mayor actividad de 10:00 a 11:00 h y de las 18:00 a 20:00 h. Los patrones de actividad temporal presentaron similitud en dos de los cuatro periodos de muestreo (P > 0.05), lo que indica que los patrones de actividad se mantienen independientemente de la cantidad de horas luz. En contraste, la actividad de las chachalacas fue diferente en el invierno de 2012-2013 (P < 0.05), posiblemente como respuesta a la presencia de elementos exógenos no climáticos, como depredadores. Durante los diseños de muestreo para estudios poblaciones se deben considerar los patrones de actividad de las especies de crácidos para entender su biología y contribuir a las estrategias de manejo y conservación.

Characterization of the melanopsin gene (Opn4x) of diurnal and nocturnal snakes

BackgroundA number of non-visual responses to light in vertebrates, such as circadian rhythm control and pupillary light reflex, are mediated by melanopsins, G-protein coupled membrane receptors, conjugated to a retinal chromophore. In non-mammalian vertebrates, melanopsin expression is variable within the retina and extra-ocular tissues. Two paralog melanopsin genes were classified in vertebrates, Opn4x and Opn4m. Snakes are highly diversified vertebrates with a wide range of daily activity patterns, which raises questions about differences in structure, function and expression pattern of their melanopsin genes. In this study, we analyzed the melanopsin genes expressed in the retinas of 18 snake species from three families (Viperidae, Elapidae, and Colubridae), and also investigated extra-retinal tissue expression.ResultsPhylogenetic analysis revealed that the amplified gene belongs to the Opn4x group, and no expression of the Opn4m was found. The same paralog is expressed in the iris, but no extra-ocular expression was detected. Molecular evolutionary analysis indicated that melanopsins are evolving primarily under strong purifying selection, although lower evolutionary constraint was detected in snake lineages (ω = 0.2), compared to non-snake Opn4x and Opn4m (ω = 0.1). Statistical analysis of selective constraint suggests that snake phylogenetic relationships have driven stronger effects on melanopsin evolution, than the species activity pattern. In situ hybridization revealed the presence of melanopsin within cells in the outer and inner nuclear layers, in the ganglion cell layer, and intense labeling in the optic nerve.ConclusionsThe loss of the Opn4m gene and extra-ocular photosensitive tissues in snakes may be associated with a prolonged nocturnal/mesopic bottleneck in the early history of snake evolution. The presence of melanopsin-containing cells in all retinal nuclear layers indicates a globally photosensitive retina, and the expression in classic photoreceptor cells suggest a regionalized co-expression of melanopsin and visual opsins.

Temporal coexistence in a carnivore assemblage from central Mexico: temporal-domain dependence

Species coexistence at a given locality generally implies segregation along one of the three resource dimensions of the ecological niche: spatial, trophic or temporal. Temporal activity patterns of species are ecologically important as they expose how species exploit their environments. Using camera traps, we evaluated the temporal activity patterns and temporal overlap for a mammalian carnivore assemblage from Sierra Nanchititla Natural Park, central Mexico. We characterized and compared temporal activity patterns and temporal overlap between species pairs using circular statistics. Temporal overlap was analyzed using three temporal domains (full diel, diurnal, and nocturnal), and null models were used to contrast the empirical assemblage-wide temporal overlap in relation to randomly generated distributions. We found that pair-wise temporal overlap comparisons among species were quite heterogeneous and dependent on the temporal domain used for the analyses. Two major inferences can be derived from pair-wise analyses and the null model: (a) most of the carnivore assemblage show a nocturnal activity pattern in common and (b) most of the pair-wise comparisons indicate temporal segregation among species. The highest temporal overlap at the assemblage-wide level was found when only the nocturnal domain was evaluated and we found coincident temporal activities at the full domain level, independent of the temporal resolution used. Overall, our results suggest that carnivores with distinct trophic and habitat use like the margay (Leopardus wiedii) and gray fox (Urocyon cinereoargenteus) had temporal overlapping activity patterns to full diel and nocturnal domains, and species with similar trophic and habitat use always presented temporal segregation (gray fox and white-nosed coati, Nasua narica). Finally, species with predator-prey relationships (white-nosed coati and cougar, Puma concolor) showed segregation during the day but overlap at night. Our results indicate that species temporal activity patterns likely change in relation to different interspecific interactions such as predation and competition to allow species coexistence within this carnivore assemblage.