Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

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An overview of population density control in social mammals sets the framework for examining reproductive responses to increasing population densities.  We begin by honoring John B. Calhoun who played a major role, starting about 70 years ago, in correcting the conventional wisdom of the time that population control was all about adjusting mortality rates.  Reproduction was considered a constant, and emigration was viewed as a component of mortality.  His research was mostly on domestic and feral populations of Rattus norvegicus and Mus musculus for which he built complex arenas that could house thousands of inhabitants.  In addition, he constructed elaborate living quarters in the alleyways of Baltimore.  For the captive populations, he would individually mark all the inhabitants so that he could identify them and observe their behavior.  Eight examples of his research publications are described.  He was able to document a list of reproduction related behaviors that are the main focus of this essay, and clearly demolish the simplistic notion that reproduction is a constant.  A summary of some of the major issues that encompasses the science of population growth and regulation is provided.  There follows a series of 19 examples of non-Calhoun publications that cover many more species of social mammals, including humans.  A comprehensive list of the many negative adaptations involving reproductive processes are documented for the 27 publications reviewed confirming that in many species reproductive constraints are non-trivial.  There follows a brief discussion that attempts to create a cohesive whole for this intellectual adventure.

A reduction in the frequency of rainfall and an increase in drought periods, as a consequence of climatic change, has caused the desiccation of water ponds (locally known as “aguadas”) in the Calakmul region. The objective of this study was to determine if the abundance and distribution of the white-lipped peccary, Tayassu pecari, and the collared peccary, Pecari tajacu, in the ponds of the Calakmul Biosphere Reserve, a tropical forest in Southern México, are related to water availability and to the presence of their predators throughout five years of study. Using photo-trapping technique, 12 aguadas were monitored. The index of abundance of photographic records and the activity patterns were estimated, and the presence of both species of peccaries was related through linear and logarithmic regressions with the availability of water and their predators (pumas and jaguars). The abundance and presence of the white-lipped peccary and the jaguar were directly related to decreasing water availability, while water was not a determining factor for the presence of the collared peccary and the puma. The decrease in the availability of water in the aguadas of the reserve has become a serious threat to the white-lipped peccary, one that, when coupled with other threats such as hunting and fragmentation of their habitat in the communities surrounding the reserve, will increase the risk of extinction of these populations, that at least for the white-lipped peccary, is the most important in Mesoamerica.

A new method of studying for activity of a semi-aquatic mammal Russian desman Desmana moschata (Linnaeus, 1758) with use of digital portable voice recorders is developed. To identify the burrows in which the recorders were to be installed, the burrows were probed. A probe is a pole pointed at one end with a T-shaped handle at the other end. The researcher’s task was to detect the entrance to the burrow, usually under water. The direction of the underground passage is determined by means of the probe. For this purpose, the ground is pierced to detect the hollows in the burrow with the probe starting from the burrow entrance (the probe falls through unevenly). At a distance of 2 to 3 meters from the burrow, in some cases largely depending on the burrow length, the ground is dug up above the burrow in the form of a small well, 10 to 15 cm in diameter. A digital voice recorder was placed vertically in this well, so that the microphone was directed down towards the burrow. Desman noises can be characterized as short series formed as a sequence of contiguous short peaks of 15 to 25 seconds with five second interruptions formed by regular waves of breathing and its movement noises. As a rule, the noise audibility ranges from 1 to 3 minutes.

Neotropical otters have been scarcely studied at the northern edge of their distribution in Mexico.  The species has nocturnal-twilight habits, and their principal food is fish and crustaceans.  The aim of this work was to know the foraging habits of Neotropical otters (Lontra longicaudis) in two monitoring sites one lentic and the other one lotic systems of the Río San Lorenzo, Sinaloa México.  From February 2009 to January 2010, we surveyed the area during the four seasons by walking 15 km of the river edge of Río San Lorenzo, and 15 km at the El Comedero reservoir.  We collected 318 scats, 155 in the reservoir and 163 in the river.  Fish were the most abundant prey item in both places, with a frequency of occurrence of 98.1 % in the river and 100 % in the reservoir.  The percentage of occurrence varied largely in the other prey items in both places.  Seven taxonomic groups compose their foraging habits in the river (relative frequency in parentheses): fish (64.3 %), insects (9.2 %), mollusks (6.8 %), birds (6.0 %), mammals (5.6 %), crustaceans (5.2 %) and fruits (2.8 %).  Five taxonomic groups in the reservoir compose it: fish (65.1 %), birds (22.7 %), mammals (9.2 %), fruits (2.5 %) and insects (0.4 %). The most important fish in the diet belonged to the genus Oreochromis, which includes an introduced species.  We conclude that the Neotropical otter is an opportunistic carnivore that preys mainly on fish, probably due to their high availability, but they also forage in other taxa that are available at Río San Lorenzo basin.

Small mammal populations can be affected by habitat degradation, causing changes in their abundance, density and movement.  Akodon montensis, a persistent host for Orthohantavirus, is a common rodent species in primary and secondary forest habitats and is considered a generalist species.  This paper analyzes how habitat degradation and resource availability affect the population characteristics of the species.  Six plots were classified into three levels of degradation, with sampling conducted in June and November 2015.  After the June sampling, three plots were selected for the increase of food resources for three months, to assess how this factor affects the population.  Abundance was estimated with the capture-mark-recapture method and density was estimated by dividing abundance by the effective sampling area.  Home range was calculated using the Minimum Convex Polygon method, and the Maximum Distance Traveled as the longest average movement between two sampling stations where an individual was encountered.  More degraded habitats supported lower average density and abundance of A. montensis compared to less degraded habitats. Increasing food availability led to increases in abundance in the more degraded habitats and decreases in the least degraded.  Changes in home range were most evident, decreasing in the least degraded plots after the increase in resources.  The sex ratio did not differ from equity in any plot, nor with respect to any of the factors studied.  Population characteristics of the species are determined by several factors, including habitat quality and food distribution and abundance.  If changes occur in these factors (either artificially or naturally) then movement, abundance and population density are affected in response to such changes.  Although some results were not statistically significant, an apparent interaction was observed between habitat quality and resource availability, thereby influencing the abundance and density of A. montensis. 

The present work provides an updated checklist of helminth species infecting invasive murid rodents (Mus musculus, Rattus norvegicus, R. rattus, and Rattus sp.) in Mexico, including 35 helminth taxa (3 trematodes, 7 cestodes, 2 acanthocephalans, and 23 nematodes).  The helminthological records were compiled from 18 studies conducted in seven Mexican states up to May 2020.  Information on habitats, life stages, geographical locations, hosts, helminthological collections, prevalences, and bibliographic references are included, when available.  Finally, a new locality record of the nematode Hassalstrongylus musculi in Yucatan is provided.

The genus Ctenomys consists of about 70 species and in addition to the Geomyidae of the Nearctic, Neotropical tuco-tucos represent a well-documented case of diversification in the subterranean biotype. Here we will: i) Provide an updated summary of the natural history of the 12 species of extant tuco-tucos from Bolivia; ii) Update information on distributions of each species; and iii) Using ecological niche modeling, evaluate recent and projected habitat transformation or habitat degradation within the known range of each species to provide a preliminary assessment of the preservation or conservation status of ctenomyids within Bolivia.  We follow Gardner et al. (2014) and combine species summaries with both updated published and new data to compile a complete list of known extant species of tuco-tucos from Bolivia.  Occurrence data for Ctenomys in Bolivia and surrounding areas were extracted from the database Arctos and GBIF.  All individual specimen-based locality records were checked and georeferenced by referring to original museum collection records. We created species distribution models for the species with enough locality records using climate and soil data, while for the rest of the species we estimated the ranges based on the known occurrence localities. Finally, we quantified the amount of large-scale habitat conversion occurring within each species range, as well as the potential effect of climatic change on species distribution.  Here we present information regarding the biology of tuco-tuco (Ctenomys) species known to occur in Bolivia, including unpublished natural history data such as habitat association, interactions and activity patterns gathered by the authors through extensive field work. Besides this, we estimated the current distribution of Ctenomys species, quantified large-scale habitat transformation within each species range and assessed the potential effect of climatic change on five tuco-tuco species. We found that the habitats within the ranges of C. boliviensis and C. steinbachi have experienced significant land-cover conversions in recent years.  We also show that C. opimus, as well as the above mentioned species are expected to undergo range contractions resulting from climatic change by 2070.  Our review shows that there is a dearth of information regarding natural history, taxonomy and distribution for many Bolivian tuco-tuco species. Nonetheless, the information presented here can be a tool for directing and focusing field studies of these species. This is of great importance if we take into account that most of the Bolivian tuco-tucos are subject to one or several conservation/preservation threats.  These include: Habitat destruction via land use or climatic changes in conjunction with geographic ranges of Ctenomys that are small in areal extent and which in many cases are not adequately covered by protected areas.

Home range is an aspect of ecology that allows us to understand the mechanisms and spatial relationships that underlie habitat choice and animal responses to environmental change. However, studies on this subject have been focused mainly on medium and large mammals, while those on small mammals are scarce.  Small mammals play important roles in maintaining ecological processes, such as the survival of several plant species. Phyllotis osilae is a phyllotine rodent, which functions as a potential seed disperser for Polylepis subtusalbida, a tree that is endemic and categorized as Vulnerable (VU) for Bolivia. The forests of P. subtusalbida are highly fragmented, with reforestation with introduced species such as Pinus radiata and Eucalyptus globulus. The question we pose for this study is: how does the home range of P. osilae vary between fragments of P. subtusalbida with different types of matrix (natural grassland and exotic tree plantations)? The study was carried out on four fragments of P. subtusalbida in Tunari National Park in the city of Cochabamba, Bolivia: two fragments in the exotic tree plantation matrix (Pajcha locality) and two in the natural grassland matrix (San Miguel locality). For telemetry purposes, radio collars were installed on 16 individuals. The home ranges were calculated using the Minimun Convex Polygon (MCP) at 95 %, in the same way the Kernel density (KDE) was estimated at 95 %. The percentage of presence of P. subtusalbida and matrix trees within each home range was determined, with an area interval between 50.5 m2 and 3,010 m2. No significant differences were found between both matrices regard to the area of activity; however, in the comparison of the percentages of presence of P. subtusalbida trees and matrix, significant differences were found. Our results for home ranges show that the matrix would not have an effect on the area, but on its mobility; this is evidenced by the absence of movements of P. osilae from the fragments to the exotic matrix. In this case, the exotic tree matrix is operating as a barrier and is reflected in the almost total absence of this vegetation matrix in the home range. P. osilae may be playing an important role in the recovery and conservation of these ecosystems, so knowing aspects of their natural history as well as their responses to fragmentation is of great importance in understanding the fate of the Polylepis forests.