Monarch butterflies (Danaus plexippus) fuel their migration and overwinter energy needs through accumulated fat stores derived from plant nectars. Determining origins of these fuels is crucial to effective conservation programs. We used stable-hydrogen (δ²H) and carbon (δ¹³C) isotope measurements in stored lipids of monarchs raised under laboratory conditions as a proof of principle for the isotopic spatial sourcing of stored lipids. We then applied this approach to wild specimens collected from 2015 to 2018 to infer spatial information on nectaring by fall migrants through northeast Mexico and at the Mexican overwinter sites. Migrating monarchs derived from wide geographic natal origins but lipid δ²H values from migratory cohorts were not related to natal origin. Instead, migrants exploited isotopically similar nectar sources. Distributions of lipid δ²H values in overwintering monarchs were broader and more negative by ∼40‰ suggesting more transport of lipids from higher latitudes or additional nectaring while migrating at higher elevations though northeastern to central Mexico. Our work establishes a new isotopic technique for tracking origins of stored lipids in monarchs and other migratory animals and emphasizes the importance of nectar availability in the southern portion of the range, and especially the nectar corridor through central Mexico.

Interspecific interactions among tropical mesocarnivorous species and other mammalian trophic guilds have been poorly studied, despite they have important implications in the survival, structure, demography, and distribution of these species. In this study we analyzed spatio-temporal interactions of three sympatric mesocarnivores that are located in the Northeastern limit of their geographic distribution in Mexico, with the objective of analyzing if these species coexist or compete in the axis of the temporal and spatial niche. With a sampling period from January 2015 to December 2016 and 26 camera-trapping stations (with in a set of two camera traps opposite to each other) and located along roads and animal trails, we determined the activity pattern and habitat use of L. wiedii (margay), L. pardalis (ocelote) y P. yagouaroundi (yaguarundi). All independent photographs of each species were grouped into three temporal categories (day, night and twilight) and six habitat categories; Oak Forest, Oak-Pine Forest, Cloud Forest, Pine-Oak Forest, Tropical Deciduous Forest and Medium Forest. Temporal and spatial overlap between species (i.e interactions) was obtained with the Czekanowski index and the Pianka index, respectively. These indices are symmetrical and take values from zero to one, where the results close to zero indicate that there is no overlap between species and values close to one indicate overlap. We obtained a total of 379 independent photographs, of which 239 corresponded to margay, 118 to ocelot and 22 to yaguarundi. Margay and ocelot were nocturnal, with 75 % of their records in this category showing a high temporal overlap (0.85); whereas yaguarundi was fully diurnal, suggesting it may be able to coexist with the other two species (margay and ocelot). Moreover, the yaguarundi used habitat similar to ocelot and margay (with high spatial overlap of 0.81 and 0.72, respectively), while the spatial overlap between the margay and ocelot was intermediate (0.53), since they used in most cases different habitat types. Our results suggest that there is no interspecific competition among these tropical mesocarnivorous species, probably due to antagonistic interactions among them on the temporal and spatial axis. These strategies may positively favor populations of mesocarnivores, which are characterized by having a high territorial behavior.

Information on the ecology of jaguars (Panthera onca) in “El Cielo” Biosphere Reserve in Tamaulipas, Mexico is scant and limited to anecdotic records in a handful of publications. The objectives of our study were to: a) determine population density and structure of jaguars, b) compare their activity patterns with that of pumas (Puma concolor), c) ascertain potential prey relative abundance, and d) evaluate local resident’s perception on loss of domestic animals due to jaguar predation. Between April 2013 and April 2014 we conducted camera trapping in Gomez Farias Township with a total sampling effort of 8 580 camera trap days. Besides, we completed 136 semi-structured interviews among local residents of Gomez Farias and Llera Townships to gather information on domestic animal losses attributed to jaguars and other carnivores. We identified eight different jaguar individuals during a complete year of camera-trapping, composed of four adult females, one juvenile female, two adult males and one juvenile male. We estimated a jaguar density of 5.9 ± 1.3 jaguars/100 km². Activity patterns for jaguars and pumas were similar as both were nocturnal and crepuscular in nature. The most abundant potential prey species for jaguars in the study site were Crax rubra, Cuniculus paca, Mazama temama, Odocoileus virginianus and Didelphis virginiana; while the rarest were Mephitis macroura and Procyon lotor. Interview results suggested that chickens, dogs, and house cats were the most consumed domestic animals from all reported losses by local residents (n= 107). This study represents the first attempt to describe jaguar ecology in “El Cielo” Biosphere Reserve; however, there is a need of additional monitoring efforts to determine the current status of jaguars in a larger area in order to establish conservation strategies. Finally, this jaguar population may have an important role in maintaining the species in the Sierra Madre Oriental biological corridor connecting populations in Nuevo Leon and San Luis states in Northeastern Mexico.

The eastern population of the North American monarch butterfly (Danaus plexippus) overwinters from November through March in the high-altitude (3000 m+) forests of central Mexico during which time they rely largely on stored lipids. These are acquired during larval development and the conversion of sugars from floral nectar by adults. We sampled fall migrant monarchs from southern Canada through the migratory route to two overwintering sites in 2019 (n = 10 locations), 2020 (n = 8 locations) and 2021 (n = 7 locations). Moderate to extreme droughts along the migratory route were expected to result in low lipid levels in overwintering monarchs but our analysis of lipid levels of monarchs collected at overwintering sites indicated that in all years most had high levels of lipids prior to winter. Clearly, a significant proportion of lipids were consistently acquired in Mexico during the last portion of the migration. Drought conditions in Oklahoma, Texas and northern Mexico in 2019 resulted in the lowest levels of lipid mass and wing loading observed in that year but with higher levels at locations southward in Mexico to the overwintering sites. Compared with 2019, lipid levels increased during the 2020 and 2021 fall migrations but were again higher during the Mexican portion of the migration than for Oklahoma and Texas samples, emphasizing a recovery of lipids as monarchs advanced toward the overwintering locations. In all 3 years, body water was highest during the Canada—USA phase of migration but then declined during the nectar foraging phase in Mexico before recovering again at the overwintering sites. The increase in mass and lipids from those in Texas to the overwintering sites in Mexico indicates that nectar availability in Mexico can compensate for poor conditions experienced further north. Our work emphasizes the need to maintain the floral and therefore nectar resources that fuel both the migration and storage of lipids throughout the entire migratory route.

Although the ocelot Leopardus pardalis is listed as endangered in the USA and Mexico, research on the characteristics of ocelot populations in northeastern Mexico has been limited. Effective conservation strategies in this binational region can benefit from additional information on the distribution and status of these populations. We estimated ocelot abundance and density using capture-recapture data from remote cameras at 2 locations in Tamaulipas: 1 inland site near the Sierra Tamaulipas and 1 coastal site along the Laguna Madre. The inland site was sampled in 2013 with 32 camera stations, and estimated densities (mean ± SE ocelots per 100 km²) using non-spatial and spatial modeling approaches were 17.57 ± 1.10 and 28.19 ± 6.81, respectively. The coastal site was sampled in 2017 with 16 camera stations, and estimated densities using non-spatial and spatial modeling approaches were 59.03 ± 2.32 and 43.24 ± 7.24, respectively. These are the first published ocelot densities for these locations, and these sites represent the closest known populations to those in Texas, USA. The ocelot populations surveyed appear to be robust, with estimated abundances similar to or greater than other areas surveyed within the state of Tamaulipas. Future work should monitor the long-term status and connectivity of these and other nearby populations to inform management actions to ensure their continued existence, as well as to assess whether they could serve as suitable sources for the translocation of individuals into existing populations in need of genetic rescue in Texas.

Context: Road networks are related to two global problems: habitat loss and degradation, and the decline of biodiversity. Wildlife roadkill is one of the most obvious and immediate impacts of linear infrastructure that affects all vertebrate groups, and some species, such as large carnivores, are more susceptible to fragmentation by roads due to their wide-ranging movements and home ranges. Aims: Recently, black bear (Ursus americanus) sightings have increased in urban and suburban areas. The objectives of this study were: to identify and characterise road crossing sites used by black bears; to understand whether bears select specific landscape or road features for crossing; to compare crossing and roadkill sites; and to identify the most important variables in both groups to propose short-term mitigation strategies. Methods: For the analysis of crossing sites, black bear individuals were captured from 2014 to 2018 and released with a GPS collar. We also calculated the dynamic model of Brownian motion to identify the road crossing sites. We obtained collision records from field work and government agencies. We performed Firth’s penalised-likelihood logistic regression models to identify the most important variables of highway or landscape in the probability of crossing or roadkill. Key results: We captured 15 black bear individuals (11 males and four females), seven of which crossed a road at least once. Most of the crossings occurred during the night, which explains the results of the regression model between crossing and roadkill sites because crossings are a function of the percentage of buses and urban use. We also found that the speed at roadkill sites is significantly higher than at crossing sites. Conclusions: This study contributed aspects necessary to understand the management of highways and reduce their impact on the black bear population in Mexico, such as the identification of priority mitigation sites. Systematic monitoring of roadkill in Mexico is required to propose specific mitigation sites that will benefit more vertebrate groups. Implications: The information generated in this research forms the basis of identification of optimal sites for strategies to mitigate the bear–road conflict and help the conservation of the species.