Comparing radio-tracking and visual detection methods to quantify group size measures

1. Average values of animal group sizes are prone to be overestimated in traditional field studies because small groups and singletons are easier to overlook than large ones. This kind of bias also applies for the method of locating groups by tracking previously radio-collared individuals in the wild. If the researcher randomly chooses a collared animal to locate a group to visit, a large group has higher probability to be selected than a small one, simply because it has more members.2. The question arises whether location of groups by means of finding collared animals has smaller or greater bias than searching for groups by visual observation. If the bias is smaller or same, this method can be recommended  for finding groups. However, such a comparison cannot be made by speculation, only by empirical investigation.3. The present study compares the two methods empirically, by statistically comparing group size measures (mean, median, quantiles, frequency distribution, and ‘typical group size’) between two data sets. These data sets  comprise of Rocky Mountain mule deer group size values collected in the same area during the same period of time, referring either to groups located by the traditional ‘search and observe method’ or located by tracking formerly collared individuals.4. All group size measures are statistically similar in the two samples, thus we conclude that the two methods yielded similar biases. Although the true group size measures are not known, we presume that both methods have overestimated them. We propose that these results do not necessary apply to other species, thus cannot be generalized. The reason for this is that bias may depend on factors specific to the species: bias of visual observation may depend on how well the species conceals itself in the existing habitat, and the bias associated with finding groups using collared animals is likely dependent on group size distribution and also on the proportion of collared animals in the population

Insectos de la "una de gato" (Uncaria guianenesis y U. tomentosa : Rubiaceae), planta medical de la Amazonia peruana

Two species of #Rubiaceae$ known as "una de gato", vernaculate name, are medicinal plants very used in the Peruvian Amazonia. Its excessive exploitation in the natural environment has made its cultivation necessary. Different species of phytophagous insects have been observed on "una de gato" in an experimental plantation in Iquitos, Peru. (Résumé d'auteur

The Unionid Mussel Fauna of Northeastern Ohio’s Grand River

Author Institution: Environmental Studies Program, Hiram College, OHAuthor Institution: Dept. of GBES, Cleveland State University, OHAuthor Institution: EnviroScience, Inc., Stow, OHAuthor Institution: Hiram College, OHUnionid mussel distribution, numbers, and species were examined in the Grand River to provide a recent and comprehensive study of mussels from northeast Ohio’s longest river. The entire length of the Grand was canoed and examined for unionid mussel beds, with the exception of upstream areas where the river was small; SCUBA was used to survey just upstream of Fairport Harbor. The lower river, designated Grand River’s Wild and Scenic section, was studied in 1995, the middle reaches, called the Scenic section, were surveyed in 1996, and completion of the headwater region followed in 1998. Finally, a survey near the mouth of the river was made in 2002. A total of 95 sites were examined visually, by hand, with bottom sieves, dip nets, or by diving, as conditions demanded; riverbanks were searched for dead shells. A total of 11,625 living mussels and 4,514 dead shells comprising 27 species were identified. All species found were represented by living specimens. Comparisons to earlier collections indicated that the unionid fauna is changing, especially in downstream areas, but the diversity of these threatened acroinvertebrates in the Grand River has been much less affected than in the neighboring Ohio rivers to the west