Ivan Castro-Arellano

Effects of Habitat Conversion on Temporal Activity Patterns of Phyllostomid Bats in Lowland Amazonian Rain Forest

Abstract Ecological assessments of the effects of anthropogenic change often focus on species richness or species abundances. Nonetheless, changes in behavior (e.g., activity patterns) may provide equally important insights into responses to disturbance that have conservation or management implications. Because many neotropical bats provide critical ecosystem services, their responses may be of particular conservation concern. We evaluated the effects of season and habitat conversion on temporal activity patterns of 8 abundant species of frugivorous bats in lowland tropical rain forest of Iquitos, Perú. Season had little effect on activity patterns of any species of bat. Five species exhibited different activity patterns in primary or secondary forest compared to agricultural habitats. No interspecific differences in activity patterns occurred in primary forest. In agricultural areas, the patterns of activity of Carollia benkeithi and Rhinophylla pumilio were distinct from those of other species. In secondary forest, activity patterns of Artibeus lituratus and R. pumilio were distinct from those of other species. Temporal activity patterns of common frugivores overlapped more than expected by chance, regardless of season or habitat. Neotropical frugivores avoid open areas during twilight to reduce risk of predation. Nonetheless, to meet their considerable minimum daily caloric intake requirements, frugivores forage throughout most of the night. Increased habitat fragmentation may effectively reduce foraging times and subject bats to increased risk from predators during twilight and periods of great lunar illumination, when bats avoid open areas.

Temporal niche segregation in two rodent assemblages of subtropical Mexico

Temporal niche partitioning can be a viable mechanism for coexistence, but has received less attention than other niche axes. We characterized and compared patterns of activity, and overlap of temporal activity among the five common rodent species from a tropical semideciduous forest (TSF) and between the two common rodent species from cloud forest (CF) at El Cielo Biosphere Reserve in Mexico. Capture frequencies over 2-h intervals, obtained via live trapping (6850 trap-nights) in chosen months over 3 y formed the empirical basis for analyses. Trap transects were set from 19h00 to 07h00 and checked every 2 h. Analyses of 484 captures evinced two distinct assemblages. The TSF assemblage was diverse and with non-random temporal niche segregation, whereas the CF assemblage was depauperate with its two dominant species evincing the same activity pattern. Predator avoidance between open- and closed-microhabitat species, as well as niche complementarity may explain temporal segregation at TSF. This is the first documentation of assemblage-wide non-random temporal segregation of neotropical rodents. Time of activity may be a largely under-appreciated mechanism in other species-rich tropical rodent assemblages as well as in other species-rich biotas.

Survey for antibody to hantaviruses in Tamaulipas, Mexico.

Wild rodents (n=248) were trapped in two ecologically distinct sites at El Cielo Biosphere Reserve in the state of Tamaulipas, Mexico, during the summer of 2003. Samples from 199 individuals were tested for Hantavirus antibodies by an indirect enzyme-linked immunosorbent assay (ELISA). Hantavirus antibodies to recombinant Sin Nombre virus nucleocapsid protein were found in seven rodents (3.5%) of a single species, Peromyscus levipes. Antibody-positive rodents were found only in the Cloud Forest site, which had lower rodent species diversity than the Tropical Subdecidous Forest site. Although the identity of the virus in P. levipes remains to be determined, our study provides further evidence that Hantavirus antibody–positive individuals are prevalent in the rodent fauna of Mexico. This is the first survey for Hantavirus antibodies in the rodent fauna of Tamaulipas and the first report of P. levipes as a potential host for a Hantavirus.

Unusual temporal niche overlap in a phytophagous bat ensemble of western Cuba

We assessed the differences and similarities in diel activities among five phytophagous bat species at two habitats over two seasons within the Sierra del Rosario Biosphere Reserve in Cuba. We characterized temporal patterns of activity and overlap of temporal activity for frugivore and nectarivore bat species (Artibeus jamaicensis, Monophyllus redmani, Phyllonycteris poeyi, Phyllops falcatus and Brachyphylla nana) that occur in tropical evergreen forest sites with distinct altitude and vegetation structure during wet and dry seasons. Capture frequencies using mist-nets of 1180 capture events were the empirical basis for analyses. For each species we compared activity patterns between habitats, between seasons, between males and females, as well as between reproductive and non-reproductive females. We also assessed temporal overlap among each possible pair of species at each habitat and used Monte Carlo simulations to evaluate assemblage-wide temporal niche overlap using a new algorithm, termed Rosario, designed specifically for temporal data. The two habitats had the same species composition and bat diel rhythms tended to be consistent across habitats, seasons and sexes for most bat species. In general bat species pairwise temporal niche overlap was high. and the ensemble-wide temporal overlap was consistently high across habitats and seasons indicating a common constraint for bat activities. Activity peaks of most bat species coincided at 4-5 h after sunset, this being in sharp contrast to other Neotropical bat assemblages at continental sites where activity peaks usually overlap within the first 2 h after sunset. This strong disparity in timing of activity peaks between continental and insular bat assemblages can provide the framework for the generation of hypotheses that explain the potential role of time as a mediator of ecological interactions in bat assemblages.

Antibody Seroprevalence to Hantaviruses in Rodents from Reserva De La Biosfera Sierra De Huautla, Morelos

ABSTRACT. Hantavirus pulmonary syndrome (HPS) is a rare disease with a high mortality rate, caused by New World viral species of the genus Hantavirus. The presence of hantaviruses both north and south of Mexico suggests an extended presence through the country. Our objective was to conduct serologic tests to detect antibodies against hantaviruses in wild rodents of the tropical deciduous forest in Morelos, Mexico, and to report information about the distribution and prevalence of these viruses. Blood samples from 153 cricetid and heteromyid rodents were tested for immunoglobulin G (IgG) antibodies. One individual of Liomys irroratus was seropositive for a Hantavirus antigen. Our results suggest that hantaviruses occur in rodents from southern Morelos in central Mexico. Given the possibility of a false positive result, it is important that this finding be validated with further research.

Is species richness driving intra- and interspecific interactions and temporal activity overlap of a hantavirus host? An experimental test

High species diversity of the potential animal host community for a zoonotic pathogen may reduce pathogen transmission among the most competent host, a phenomenon called the “dilution effect”, but the mechanisms driving this effect have been little studied. One proposed mechanism is “encounter reduction” where host species of low-competency decrease contact rates between infected and susceptible competent hosts, especially in directly transmitted diseases. We conducted an experiment in outdoor enclosures in northwestern Mexico where we manipulated rodent assemblages to assess the effect of species richness on the frequency of intra- and interspecific interactions and activity patterns of a hantavirus reservoir host (North American deermouse; Peromyscus maniculatus). Trials consisted of three treatments of rodent assemblages that differed in species richness, but had equal abundance of deermice; treatment 1 consisted of only deermice, treatment 2 included deermice and one non-competent host species, and treatment 3 included two non-competent host species in addition to deermice. To measure interactions and temporal activity, we strategically deployed foraging stations and infrared cameras. We did not find differences in the frequency of intraspecific interactions of deermice among treatments, but there were significantly more interspecific interactions between deermouse and non-competent hosts in treatment 2 than treatment 3, which is explained by the identity of the non-competent host species. In addition, there were differences in activity patterns between rodent species, and also between deermice from treatment 1 and treatment 2. These results indicate that at least at a small-scale analysis, the co-occurrence with other species in the study area does not influence the frequency of intraspecific interactions of deermice, and that deermice may be changing their activity patterns to avoid a particular non-competent host species (Dipodomys merriami). In conclusion, in this deermouse-hantavirus system a potential dilution effect would not be through intraspecific encounter reduction in the most competent hantavirus host. To identify variables of host assemblages that can influence pathogen transmission, we highlight the need to address the identity of species and the composition of assemblages, not only host species richness or diversity.