Bat ecology and conservation in semiarid Mediterranean landscapes (original) (raw)
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Acta Zoologica, 2012
Although sexual size dimorphism (SSD) is common among mammals, there is no clear explanation for its maintenance in nature. Bats are one of the few groups of mammals where reverse SSD appears. In this group, the size of individuals may have very important ecological consequences related with flight. In this study, we examine sexual dimorphism in the wing measurements of 195 adult individuals (141 males and 54 females) of the greater mouse-eared bat Myotis myotis in the southeast of the Iberian Peninsula. We also investigated size differences between paired and single males in a swarming roost. The results indicate that there are significant differences in the wing measurements between sexes, females being bigger than males in this respect. While no significant differences in the wing measurements of paired and single males were observed, significant differences were found in their relative weight and fitness, single males being significantly heavier and having a better physical condition. We discuss the implications of SSD for the female of M. myotis in terms of reproductive advantages, trophic niche segregation and a greater ability to move, which may favour gene flow between populations.
Bridges over the troubled Conservation of Iberian Bats
In the last decades the availability of roosts has been one of the ma�or limiting factors in bat conserva-the last decades the availability of roosts has been one of the ma�or limiting factors in bat conservation. Several human-made structures mimic the conditions occurring in natural roosts allowing the maintenance of bat populations and in some cases, even their range expansion. In the USA and Europe several bridges have been reported to be used by bats as roosts. We surveyed 52 bridges in North-eastern Portugal and found that 28 bridges were used by bats from 16 species. Most species seem to use bridge crevices, but cave dwellers were also observed in box girders. At least 3145 individuals were found roosting in crevices, most of which were identified as Tadarida teniotis. A total of 728 individuals were captured in 8 different bridges. T. teniotis was the most common species since it was the target species of these captures. The observed sex bias toward females suggests that bridges are often used as breeding colonies. Signs of swarming and mating were also observed in September and October. Our results confirm that modern bridges can play an important role in bat conservation even contributing to range expansions.
Acta Chiropterologica, 2008
Most of the little information available on the foraging ecology of the threatened Geoffroy's bat Myotis emarginatus refers to areas outside the Mediterranean Basin. In this study, we analysed habitat selection by this species in a typical Mediterranean landscape. We radio-tracked a breeding colony (adults and juveniles) in the Iberian Peninsula and analysed habitat selection patterns. Although we confirmed the species' preference for forest, olive groves also appeared an important foraging habitat for both adults and juveniles. Juveniles proved to be less mobile than adults, moving on average 1.6 km less than adults in displacements to foraging sites and preferred more accessible habitats. We highlight here the importance of traditionally managed olive groves as foraging sites for this threatened bat. The ripping-up of ancient olive groves and their replacement by intensively managed cropland, urban areas or shrubland represents a significant threat for this vulnerable species in Mediterranean landscapes.
Taxonomy, status and distribution of the Azorean bat (Nyctalus-azoreum).
Journal of zoology, 2003
The taxonomic status of the Azorean bat i Nvctahrs (lzO/'cum Thomas 190!) was assessed, by a principal components analysis of measurements of the external morphology of the bat. together with specimens of the closest related Nyctalus species from mainland Europe (Nvctalus leislcrit. This analysis confirms the recent suggestion, based on a similar analysis of skull morphology, That the Azorean bat represents a good species, distinguished from N. leislcri by its smaller sizeforearm lengths for N. azoreuin in range 35·7-42'0 mm (11= 14). compared with 42·0-45·R mm (11 = 8) for N. leisleri. The status and distribution of the Azorean bat was assessed by a survey conducted in the Islands in September and October 1988. We assessed the presence or absence of bats, in62 (l ' latitude x l ' longitude) plots at the west end of the island of Sao Miguel. The study area covered 6% of the total land area of the archipelago and contained representative areas of all the major island habitat types. A less intensive survey throughout lour other islands. literature review and information from other sources revealed that the bat is probably distributed throughout the entire archipelago. with the possible exception of Flores and Corvo. Bats were active both in the day and at night. At night. bats were mostly active in coastal villages where they were closely associated with street lighting. During the day. most bats were active in the inland areas near to Caldeira lakes. The maximum number of bats observed simultaneously active in thc day was six whilst at dusk swarms of up to 55 (± 5) bats were observed together. At night. bats were also active over approximately ]·5 x the area they occupied in the day. By assuming the bat is found throughout the archipelago. and that our study area was representative, we estimated the maximum population to be between 1750 (from daylight activity) and 23.650 (from nocturnal activity). This latter estimate implies a fOP Illation density throughout the archipelago of around O'I bats per hectare.
Summer foraging habitats of bats in a Mediterranean region of the Iberian Peninsula
Acta Chiropterologica, 2007
Preservation of foraging habitats is a fundamental approach to bat conservation. Yet, knowledge on the primary foraging sites of Mediterranean bats remains scarce, particularly during the summer when the availability of prey can be limiting. This study was designed to determine in which habitats bats forage in Southern Portugal, during this potentially stressful period. During the summers of 1994 and 1995, bat foraging activity was monitored in representative habitat types using an ultra-sound detector. The number of feeding-buzzes and batpasses were counted and species identified through the analysis of recorded echolocation calls. None of the recorded species restricted its foraging activity to a single habitat type, but water sites were preferred by most bats. Tadarida teniotis was an exception to this habitat use. Further analysis confirmed that riparian habitats when surrounded by autochthonous broad-leaved forests seem to provide optimal foraging areas for bats during summer. Opposite, water sites within habitats resulting from intensive agriculture or forestry, provide very poor foraging areas. The typical Mediterranean landscape of Iberia, dominated by oak-woodlands and with numerous, scattered and well vegetated water sites, seems to grant optimal foraging habitat for bats during summer. However, this landscape is itself at risk. Current production demands are causing substantial land-use changes and, despite some European programmes on the preservation of Mediterranean oak woodlands and their biodiversity, the furtherance of this landscape is at stake. The preservation of traditional management strategies of oak-woodlands and associated water sites should be strongly encouraged.
Forest cover in Europe has substantially increased in recent decades, resulting in extensive secondary forest cover (ca. 10–20 years) that is too young for many specialist forest-dwelling species. In the Mediterranean region, forests have historically been logged with detrimental effects on local biodiversity. Only a few small forest patches remain untouched. Specialist forest-dwelling species are often less studied than other species due to their lower population densities and the inherent difficulties involved in sampling. In fact, some forests species have only recently been discovered or described such as the Myotis alcathoe (Alcathoe bat) and so there is a remarkable dearth of information regarding their natural history, habitat requirements and conservation status. A total of 18 M. alcathoe bats were captured and radio-tracked in a 100-year-old Mediterranean forest which led us to locate and describe 18 different tree roosts. The structural traits of each roost and the surrounding habitat were studied to unravel the factors involved in roost selection. Alcathoe bats were found roosting in a wide variety of sites (holes, cracks and under bark) and tree species. Around 70% of the roosts were found in dead or decrepit trees. However, except for roost height, no special traits were selected. Due to the maturity of some common holly Ilex aquifolium, this typically secondary bush species was often used as a breeding roost. Our results provide new insights into how old and small secondary tree species play an essential role in the conservation of certain forest species. Considering that in 20 years of bat surveys in the region, breeding colonies of this forest species have only been found in this forest characterized by its remarkable maturity (50–100 dead trees/ha), we suggest that current forest management guidelines (recommending densities of 5–10 dead trees/ha), might not be enough to ensure the presence of breeding colonies of these tree-dwelling bats.