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Cavity roost site availability and habitat use by bats in different aged riparian cottonwood stands

100%

Swystun M. B., Lane J. E., Brigham R. M.

Acta Chiropterologica

2007

tom 09

nr 1

Riparian forests provide important roosting habitat, abundant prey and access to drinking water for many bat species but to date there has been little research on the differential quality of habitats within riparian areas. We quantified the density of potential roost cavities in three age classes (i.e., young: ca. 20 years, mature: ca. 60 years, and old: ca. 100 years) of riparian cottonwood (Populus deltoides) forest stands. Bat activity was also sampled using acoustic detectors in one representative stand of each age class. Stands were situated along an 80 km stretch of the Missouri River in southeastern South Dakota and northwestern Iowa, USA. We predicted the highest density of potential roosts and the highest activity of bats to occur in the oldest age class. Contrary to our predictions, and previous work in aspen dominated upland sites, we found that the density of potential roosts was not significantly different between mature and old stands. However, there were no potential roosts in young stands. Data from guano traps verified the use of a number of cavities in both mature and old stands. Both commuting and foraging activities were highest in the mature, relative to the old and young stand. In total, our data indicate that mature and old stands represent high quality roosting habitat, with the mature being used preferentially for commuting and foraging. Trees in the oldest stands, however, are nearing the end of their lifespan and falling. Younger cohorts must therefore be retained for future recruitment of natural cavities.

The influence of residual tree patch isolation on habitat use by bats in central British Columbia

100%

Swystun M. B., Psyllakis J. M., Brigham R. M.

Acta Chiropterologica

2001

tom 03

nr 2

One forest management practice associated with logging aimed at contributing to the maintenance of biodiversity is to leave residual tree patches within cut blocks. Using Anabat bat-detectors we monitored bat activity along residual tree patch edges and clear-cut edges associated with recent clear-cuts in north-central British Columbia. We tested two hypotheses, (1) relative bat activity would be higher on the clear-cut edge than the residual patch edge, (2) relative bat activity would decrease on the residual patch edge with increasing isolation from the clear-cut edge. We sampled six pairs of edges and found no significant difference in bat activity between patch and clear-cut edges. We found a significant but non-linear relationship between relative bat activity on the patch edge with increasing patch isolation. Bat activity on the residual patch edge was highest at intermediate levels of patch isolation and lower both at patch edges close to, and highly isolated from the clear-cut edge. We postulate that the reason for this relationship is that patches act as windbreaks collecting high densities of insects making them good foraging areas but this benefit is coupled with an increased risk of prédation associated with crossing large gaps. At low levels of patch isolation bats may perceive residual patches and adjacent clear-cut edges as a continuous foraging area and thus, bat activity is evenly distributed throughout both habitats. In summary, our data indicate that patches provide localized habitat for foraging bats, however, foraging areas are only one habitat component required by bats and it remains uncertain if patches also offer suitable roosting opportunities.

Ograniczanie wyników

2 Acta Chiropterologica

2 Brigham R. M.

2 Swystun M. B.

1 Lane J. E.

1 Psyllakis J. M.

1 2007

1 2001

Wyniki wyszukiwania

Cavity roost site availability and habitat use by bats in different aged riparian cottonwood stands

The influence of residual tree patch isolation on habitat use by bats in central British Columbia