Effects of predator removal on vertebrate prey populations: birds of prey and small mammals

We studied the effects of removal of breeding nomadic avian predators (the kestrel, Falco tinnunculus and Tengmalm's owl, Aegolius funereus) on small mammals (voles of the genera Microtus and Clethrionomys and the common shrew, Sorex araneus) during 1989–1992 in western Finland to find out if these predators have a regulating or limiting impact on their prey populations. We removed potential breeding sites of raptors from five manipulation areas (c. 3 km² each), whereas control areas had nest-boxes in addition to natural cavities and stick-nests. Densities of small mammals were monitored by snap-trapping in April, June, and August, and densities of mammalian predators (the least weasel, Mustela nivalis nivalis, the stoat, M. erminea and the red fox, Vulpes vulpes) by snow tracking in early spring and late autumn. The yearly mean number of raptor breeding territories was 0.2–1.0 in reduction areas and 3.0–8.2 in control areas. Breeding raptors alone did not regulate prey populations in the long term, but probably caused short-term changes in the population dynamics of both the main prey, the sibling vole (Microtus rossiaemeridionalis) and an alternative prey (the common shrew). The densities of an alternative prey, the bank vole (Clethrionomys glareolus) decreased in raptor reduction areas, most likely due to increased least weasel predation pressure in the absence of breeding avian predators.     

Habitat selection and coexistence in small mammals of the southern Andean foothills (Argentina)

Habitat partitioning is considered one of the main mechanisms of coexistence among small mammals. This is especially evident in arid environments where resources are particularly scarce. Habitat characteristics such as vegetation heterogeneity and complexity are expected to increase species coexistence, increasing the number of microhabitats that can be occupied by species with different requirements. The Andean foothills can be considered as an ecotone between the Monte and Altoandina phytogeographic provinces as they harbor species from both. Consequently more species are thought to coexist in this area. The objectives of this study were to assess the macro- and microhabitat selection of the small mammal assemblage inhabiting the Andean foothills during wet and dry season and to determine how animals segregate environmental resources to ensure their coexistence. We found that habitat selection occurs at both scales in the Andean foothills. Two species, Eligmodontia moreni and Phyllotis xanthophygus, were capable of distinguishing among macrohabitat types, whereas all species showed habitat selection at the microhabitat scale. We registered selection during both seasons, with some overlap of resource selection during the wet season and the greatest segregation of microhabitat resources during the dry season. Therefore, this work evidence that the assembly of small mammals is sensitive to habitat structure especially in dry seasons where resources are constraints due to arid conditions of Andean foothills.     

Habitat preferences and biomasses of small mammals in Swaziland

This paper describes the distribution and abundance of small mammals in Swaziland in relation to quantified habitat features. Eighteen habitat sites were sampled at seven different locations in all four geographical regions of Swaziland. Small mammal diversity (as described by the Shannon diversity index) was positively correlated with vegetation density. A total of twelve species of rodents and seven species of shrews were captured; however, only six species were caught at more than three sites. Small mammal biomasses and densities were highest at the highveld and middleveld sites. Tall grassland at all elevations supported a high diversity of small mammals. Highveld montane forest supported a high biomass and diversity of species, while no species were captured in moist forest in the Lubombo mountains.     

Characteristics of distribution of fleas from small mammals and birds in the southern taiga of Priirtysh'ie]

The analysis of the landscape distribution of fleas from small mammals and birds in the southern taiga of Priirtishje is given. According to their abundance and faunistic composition the population of fleas from small mammals can be arranged into four groups: fleas of forest floodland landscape, those of forest-meadow floodland landscape, fleas of settlements and bogs.     

Differential trappability of small mammals in three habitats of Southeastern Brazil.

We compared the trappability of marked and unmarked individuals in species of marsupials and rodents of three tropical assemblages of small mammals in Brazil. Two studies used trapping grids, one in cerrado and the other in an Atlantic forest reserve, whereas the study in a rural area used transects. In the two studies using trapping grids, marked animals were frequently more trappable than unmarked ones, but in some species this difference was not significant. In the rural area, marked and unmarked animals did not differ significantly. The number of recaptures per resident animal was higher in the two studies using trapping grids than in the rural area where transects were used. Differences in trappability between the three studies might have been caused by differences not only in trapping design (grids vs. transects), but also in the type of trap used, bait, and habitat. Although differential trappability tends to be considered the rule in small mammals, these results suggest that trappability of marked and unmarked animals may be specific for the particular combination of sampling design, field methods, and habitat under study.     

Rapid method for estimating local biodiversity of a community of small mammals

A new method is proposed for short-term capture and estimation of abundance of small mammals employing lines of modified traps. Test capture was undertaken on the shore of Teletskoe Lake in northwestern Altai. The proposed method allows rapid estimation of the biodiversity of small mammals community. The test has proved that rodents-to-insectivores ratio of caught animals is closer to the results yielded by lines of ditches than by break-back traps. The method is less labor-consuming than the ditch trapping. The new trap is shown schematically and recommendations on its practical use are given.     

Helminth community structure in birds of prey (Accipitriformes and Falconiformes) in southern Italy

We compared helminth communities in 6 species of birds of prey from the Calabria region of southern Italy. In total, 31 helminth taxa, including 17 nematodes, 9 digeneans, 3 acanthocephalans, and 2 cestodes, were found. All helminth species were observed in the gastrointestinal tract, except for 3 spirurid nematodes. Most of the parasite species were detected in at least 2 hosts, but 13 helminth species were found in only 1 host. At the infracommunity level, the overall species richness and Brillouin's index of diversity varied by host, with the highest values in a generalist feeder, the Eurasian buzzard (Buteo buteo), and the lowest in a specialist, the western honey buzzard (Pernis apivorus). Species richness was gender dependent only in the sparrow hawk (Accipiter nisus). The helminth communities were characterized by different dominant species, namely, Centrorhynchus spp. (Acanthocephala) in the Eurasian buzzard and common kestrel (Falco tinnunculus), Parastrigea intermedia (Digenea) in the marsh harrier (Circus aeruginosus), Physaloptera alata (Nematoda) in the sparrow hawk, Serratospiculum tendo (Nematoda) in the peregrine falcon (Falco peregrinus), and Strigea falconis (Digenea) in the western honey buzzard. Statistical analyses confirmed a highly significant difference of helminth infracommunity structure among host species. We conclude that in the Calabria region of southern Italy, each of the raptor species studied is distinct in terms of its helminth communities, and more diverse feeding habits of the host correspond with richer helminth communities.     

Lifetime energy budgets in mammals and birds.

1. Two data sets for standard energy metabolism (351 and 320 species, respectively) and one for maximal lifespan (494 species) in mammals have been assembled from the literature. 2. In addition smaller data sets of active (field) energy metabolism in mammals (36 species) and in birds (25 species) have been drawn on. 3. The products of the respective regression parameters as well as the products of energy metabolism and maximal lifespan in individual species have been computed in order to estimate lifetime energy metabolism in mammals generally and in various mammalian orders. 4. It is found that lifetime energy budgets in mammals generally, whether standard or active, very systematically with body mass with slopes between 0.87 and 0.93, significantly different from unity (P less than 0.001 or P less than 0.01). 5. In birds, lifetime energy budgets, whether standard or active, vary with slopes of 0.94 +/- 0.05 and 0.88 +/- 0.09, which are not significantly different from unity (P greater than 0.1). 6. In carnivores, artiodactyls, primates and bats the slopes for lifetime standard as well as lifetime active energy budgets are not significantly different from one in any of the investigated data sets. 7. In rodents the lifetime standard energy budgets have slope significantly different from one; in marsupials one data set for lifetime standard and the one for lifetime active energy budget lead to slopes significantly different from one. 8. It is concluded from this analysis that current data do not support the hypothesis that lifetime energy budgets, whether standard or active, vary as the first power of body mass in mammals generally.(ABSTRACT TRUNCATED AT 250 WORDS)     

Habitat selection by two species of small mammals in the Atlantic Forest,Brazil: Comparing results from live trapping and spool-and-line tracking

Habitat selection by small mammals is usually evaluated using data from live trapping, which provides little information about the movements of individuals. Few studies used movement data or compared the results of different sampling methods to study habitat selection by these animals. We evaluated habitat selection by the rodent Nectomys squamipes and the marsupial Micoureus paraguayanus in the Atlantic Forest of Brazil using the spool-and-line technique. We also determined if percentage of captures reflected the amount of movements in each habitat. Habitat selection was determined comparing use and availability of five habitat types at two spatial scales (movement paths and movement areas) using compositional analysis, which allowed ranking of habitats according to their relative use by animals. The use of available habitat types was non-random for both species at both spatial scales. The two species had contrasting habitat affinities directly related to their particular habits, with N. squamipes using predominantly the stream habitat, and M. paraguayanus using mainly the restinga forest habitat. Patterns of habitat selection were similar at both spatial scales probably due to the small size of movement areas, which may not represent habitat use at a broader scale. For both species, live trapping and movement data provided the same ranking in habitat use, demonstrating that simple capture indices may be used to study habitat selection by these species across different habitat types.     

The use of small subcutaneous transponders for quantifying thermal biology and torpor in small mammals

Remote measurements of body temperature (T_b) in animals require implantation of relatively large temperature-sensitive radio-transmitters or data loggers, whereas rectal temperature (T_rec) measurements require handling and therefore may bias the results. We investigated whether ∼0.1 g temperature-sensitive subcutaneously implanted transponders can be reliably used to quantify thermal biology and torpor use in small mammals. We examined (i) the precision of transponder readings as a function of temperature and (ii) whether subcutaneous transponders can be used to remotely record subcutaneous temperature (T_sub). Five adult male dunnarts (Sminthopsis macroura, body mass 24 g) were implanted with subcutaneous transponders to determine T_sub as a function of time and ambient temperature (T_a), and in comparison to thermocouple readings of T_rec. Transponder temperature was highly correlated with water bath temperature (r²=0.96–0.99) over a range of approximately 10.0–40.0 °C. Transponders provided reliable data (±0.6 °C) over the T_sub of 21.4–36.9 °C and could be read from a distance of up to 5 cm. Below 21.4 °C, accuracy was reduced to ±2.8 °C, but individual transponder accuracy varied. Consequently, small subcutaneous transponders are useful to remotely quantify thermal physiology and torpor patterns without having to disturb the animal and disrupt torpor. Even at T_sub<21.4 °C where the accuracy of the temperature readings was reduced, transponders do provide reliable data on whether and when torpor is used.     

Habitat disturbance and small mammal richness and diversity in an Atlantic rainforest area in southeastern Brazil.

Since disturbance is an important ecological factor affecting species diversity in natural environments, the increasing human occupation rate in Brazilian Atlantic rainforest, which supports about 50% of Brazil's human population, has resulted in intense habitat degradation and fragmentation. Within this rainforest, animal and plant species have been lost at a high rate, and biological and diversity is presently vulnerable. Various animals community studies along a gradient of environmental disturbances have shown that the highest species diversities occur in habitats with intermediate levels of disturbance frequency and intensity. In the present study, which was carried out in the Atlantic forest of Ilha Grande (23 degrees 11' S and 44 degrees 12' W), an island located on the southern coast of Rio de Janeiro State, southeastern Brazil, we estimated species richness, diversity, and abundance of small mammals in three forest areas having different disturbance levels. This was done, in each of these areas and in an anthropic area that they surround, by establishing trails 200 m long, in which points were marked at 20 m intervals. The work involved a total effort of 4800 trap/nights. We also measured some habitat variables at each site in order to evaluated their disturbance levels. Our data showed that the two most conserved forests had the lower species richness and small mammal diversity, while in the anthropic area wild species were absent. The forest with an intermediary level of disturbance showed higher values for species richness and diversity, with the anthropic area presenting the highest disturbance level.     

Side effects and discontinuation of oral contraceptive use in southern Brazil

Oral contraceptives have many advantages, but sometimes also have side effects which can cause users to switch appropriately or inappropriately to less effective methods or abandon contraception. In Brazil, 2/3 of married women of childbearing age were using contraception in 1981, and 1/2 of these were using orals. Contraceptive behavior following reported side effects in users of oral contraceptives in Southern Brazil is examined in this study, in relation to diverse factors. Among 2904 currently-married women, aged 15-44, almost 75% reported that they had used the pill at some time, and of these, 45.6% were still doing so. Data on perceived side effects were gathered for all women. There was no independent medical evaluation of the effects, so the data did not necessarily represent actual prevalence of pill related problems. Women who reported problems with the pill were less likely to be current users (25%) than women who did not (65%). However, overall contraceptive prevalence was about the same in both groups (66.2% and 67.0% respectively), indicating that women who stop using oral contraceptives usually switch to another method. However, they are more likely to be using traditional methods than women in the general population, especially if they want more children. Termination of pill use varies little according to the type of problem reported. Women with problems who sought medical attention were more likely to stop using the pill, and 82.4% of women advised to stop by their physician did so, but the major factor affecting discontinuation was the reported experience of a problem. The most frequently reported problems were headaches (38.1%), nausea (34.1%), nervousness (27.9%), and vertigo (18.3%). Physician intervention should help to avoid women's abandoning oral contraceptives unnecessarily.     

Fleas of small mammals and birds in the forest-park area of the city of Novosibirsk

The distribution of fleas of small mammals and birds in the nidi of tick-borne encephalitis was analysed. 23 species were recorded from the forest-park zone. Palaeopsylla soricis starki, Amalaraeus penicilliger penicilliger, Megabothris rectangulatus, Ctenophthalmus assimilis, Hystrichopsylla talpae were dominant. They amounted to 90% of the total number of fleas. The greatest species variety of fleas was noted in afforested low-lying parts with rich species composition of hosts.     

Seasonal changes in density, demography and body composition of small mammals in a southern temperate forest

Eleven small mammal species (nine rodents and two shrews) were recorded in 16 months of trapping in the Karkloof Forest, Natal. Total densities varied seasonally, ranging from 60.7 animals/ha in the dry autumn and winter to 29.1 animals/ha at the onset of the rains in spring and early summer. Peaks in breeding coincided with high body fat and water content in the five common species during summer: in winter, when body fat and water levels were low, there was no breeding. This may be related to poor food quality at this time. Annual changes in density, breeding season and juvenile recruitment of Rhabdomys pumilio, Mastomys natalensis and Myosorex varius are the same as recorded in conspecific populations from other habitat types and do not seem modified by the habitat stability of the forest environment. Of the five common species, only Grammomys dolichurus , one of the few forest-associated small mammals in southern Africa, and Graphiurus murinus demonstrated stable, K-selectéd life-history styles.     

Alternative causes of edge-abundance relationships in birds and small mammals of California coastal sage scrub

Changes in the distribution and abundance of bird and small mammal species at urban-wildland edges can be caused by different factors. Edges can affect populations directly if animals respond behaviorally to the edge itself or if proximity to edge directly affects demographic vital rates (an "ecotonal" effect). Alternatively, urban edges can indirectly affect populations if edges alter the characteristics of the adjacent wildland vegetation, which in turn prompts a response to the altered habitat (a "matrix" or "habitat" effect). We studied edge effects of birds and small mammals in southern Californian coastal sage scrub, and assessed whether edge effects were attributable to direct behavioral responses to edges or to animal responses to changes in habitat at edges. Vegetation species composition and structure varied with distance from edge, but the differences varied among study sites. Because vegetation characteristics were correlated with distance from edge, responses to habitat were explored by using independently-derived models of habitat associations to calibrate vegetation measurements to the habitat affinities of each animal species. Of sixteen species examined, five bird and one small mammal species responded to edge independently of habitat features, and thus habitat restoration at edges is expected to be an ineffective conservation measure for these species. Two additional species of birds and one small mammal responded to habitat gradients that coincided with distance from edge, such that the effect of edge on these species was expressed via potentially reversible habitat degradation.     

Development of the clavicles in birds and mammals

Clavicles (collar bones) are variably present in mammals. Furculae (wishbones)--which may or may not be homologous with clavicles--are variably present and/or fused in birds and present in theropod dinosaurs. In this overview the development of clavicles and furculae is discussed with special attention to modes of skeletogenesis (whether intramembranous or endochondral), numbers of centres of ossification (one in chick furculae; two in murine clavicles), presence of cartilage (primary in clavicles, secondary in furculae), evidence from experimental analysis and from mutations for dependence of both clavicular and furcular growth on mechanical stimulation, and syndromes and mutations affecting clavicular development leading to both under and over development. J. Exp. Zool. 289:153-161, 2001.