Overview
The article that I chose to review is “The importance of ponds for the conservation of bats in urban landscapes” by Ancillotto et al. (2019). The study presented in the article discusses research into the importance of urban ponds and how certain qualities can shape how effectively different bat species can survive in their presence. Bats are a vital species when aiding in insect control around urban areas and while many species are heavily impaired in urban environments, there are still those that thrive in these conditions.
The goals of this study were to find how strongly differing levels of vegetation surrounding the ponds had an effect on bat populations. They also sought to record how the surrounding landscape and artificial light presence had a selective impact on bat species. These questions focused on how well bats can feel comfortable avoiding predators in an urban environment as well as how beneficial an area is to their own feeding techniques. These bats rely on lentic habitats for their high water intake so ensuring the area is suitable for preying upon insects is vital to their survival in an urban environment.
Methods
The study was taken place in the municipality of Rome across 35 selected ponds. These ponds were selected to ensure the study encompassed varying pond sizes, riparian vegetation, natural or manmade banks, and surrounding land cover. The ponds were found via satellite images and were only considered if they contained a water surface that was level with the surrounding ground, a perennial history, open air to allow bat access to the pond, the pond was not connected to any other bodies of water, and the water surface was free from vegetation. The ponds’ origins did not have any effect on their selection and for all ponds chosen there were pond management practices taken at least 2 years before the study.
For bat sampling, activity was recorded between June and September 2016-2017. Samples were taken four hours after sunset and only once per site. A manually operated Pettersson D1000X bat detector was used at each site and sampled at a frequency of 384 kHz. Recordings were taken along the banks of each site where there were no obstacles or noises that could block or interfere with readings. Weather and moon illumination were also taken into account when deciding on when to perform sampling events. From here, bat species were identified by their echolocation calls and the most abundant species was used for analysis of bat activity. Bat activity was quantified as bat passes per night with bat passes being counted with 2 or more echolocation calls.
For the second part of the experiment, the landscape and environment was estimated within 50m, 200m, 1000m, and 3000m radii of circular areas around the sampling point. Each distance aided in measuring different categories of environmental features from local to much more broad features of the area. Habitats were to be classified as urban matrix, woodland, open green areas, or intensive farmland. Finally, distance between the pond and other important features was also taken to aid in statistical analysis.
| Environmental variable | Description | Unit |
|---|---|---|
| woodland1000 | Amount of woodland habitat types in a 1000 m radius around sampling point | Percentage |
| perimeter | Measure of pond perimeter – a proxy of riparian habitat availability | Metres |
| bank type | Classification of riparian habitat as natural (>75% covered in vegetation) or artificial (>75% made of concrete) – proxy of riparian habitat quality | Categorical |
| distmargin | Distance between sampling point and closest vegetation edge (hedgerow, tree line, woodland margin) | Metres |
| distbuilding | Distance between sampling point and closest building | Metres |
| distlight | Distance between sampling point and closest artificial nocturnal light | Metres |
| green50 | Amount of open green areas (open spaces not including patches of woody vegetation such as natural grasslands, recreational green areas, non-intensive farmland, orchards, private vegetable gardens, small organic farms) in a 50 m radius around sampling point | Percentage |
| green200 | Amount of open green areas (open spaces not including patches of woody vegetation such as natural grasslands, recreational green areas, non-intensive farmland, orchards, private vegetable gardens, small organic farms) in a 200 m radius around sampling point | Percentage |
| green1000 | Amount of open green areas (open spaces not including patches of woody vegetation such as natural grasslands, recreational green areas, non-intensive farmland, orchards, private vegetable gardens, small organic farms) in a 1000 m radius around sampling point | Percentage |
| green3000 | Amount of open green areas (open spaces not including patches of woody vegetation such as natural grasslands, recreational green areas, non-intensive farmland, orchards, private vegetable gardens, small organic farms) in a 3000 m radius around sampling point | Percentage |
Results
Of the 2317 recorded bat passes, 94.4% belonged to the species Pipistrellus spp. and Hypsugo savii. The most common bat species that was found at all recorded sites was the P. kuhlii and had a total of 1049 bat passes. The results found from environmental data in addition to this species showed a positive relationship between the bats and the amount of bank habitat alongside the ponds. Another feature that was found to be important was the existence of natural banks over artificial ones. Bats were generally found to be more active around ponds with a majority of natural banks rather than those that were dominated by artificial banks. Distance from the closest building also had a consistently positive effect while distance from closest streetlamp light had varying effects from positive to negative depending on the species. This aids in the notion of how different bat species using different hunting techniques which can be harmed or helped by the presence of light. The amount of open habitat had a varying effect throughout the different species at different ranges while woodland habitat within the 1000m radius was found to have an overall positive effect.
| Response | Model | AICc | ΔAICc | k | w |
|---|---|---|---|---|---|
| Species richness | woodland1000 | 121.97 | 0.00 | 1 | 0.55 |
| woodland1000 + perimeter | 123.02 | 1.05 | 2 | 0.02 | |
| Total bat activity | perimeter + distmargin + woodland1000 | 337.71 | 0.00 | 3 | 0.65 |
| perimeter + distmargin + woodland1000 + distbuilding | 338.88 | 1.17 | 4 | 0.36 | |
| Pipistrellus kuhlii | perimeter + distlight + distmargin + woodland1000 | 286.59 | 0.00 | 4 | 0.66 |
| perimeter + distlight + distmargin + woodland1000 + green1000 | 288.44 | 1.85 | 5 | 0.15 | |
| Hypsugo savii | perimeter + distbuilding + distmargin | 248.85 | 0.00 | 3 | 0.75 |
| perimeter + distbuilding + distmargin + green50 | 249.45 | 0.60 | 4 | 0.30 | |
| perimeter + distbuilding + distmargin + green50 + bank type | 249.60 | 0.75 | 5 | 0.28 | |
| Pipistrellus pipistrellus | bank type + distmargin | 236.44 | 0 | 2 | 0.63 |
| bank type + distmargin + perimeter | 237.31 | 0.87 | 3 | 0.59 | |
| bank type + distmargin + perimeter + green3000 | 238.33 | 1.89 | 4 | 0.11 | |
| Pipistrellus pygmaeus | distlight + bank type + woodland1000 + perimeter + distmargin | 171.51 | 0 | 5 | 0.49 |
Critiques/Reflection
As a study, I found this to be an interesting topic to have questions about. Bats have always seemed to me as a species that readily benefits humans as they are a pest control species. One feature I liked about the article was its discussion on how light posed as a detriment to many species of bats while it could prove advantageous to others. The article did discuss how the light was useful in attracting prey and dangerous for revealing bats to predators but it did not give specifics as to why some bats choose to risk it. If there were to be any improvements there I would add what sort of adaptation or improvement some bats have that allows them to make use of well lit areas and reap the benefit of increased food.
For areas that could be expanded upon, the article did a great job at listing other variables that were not included but should be referenced in future studies. One example includes how water quality might have an effect on a pond’s popularity with bats. Since bats use ponds as one of their primary drinking sources, it is important to study what kind of water pH or quality they prefer. This can then be used to determine what water management practices should be taken for urban ponds as well as the vegetation that surrounds them.
A point I would like expanded is the idea that certain ponds might need to focus on benefitting one species over others. In this study, the results were compared to the preferences of the most common species. What if we should then be focusing our efforts on what the minority of species needs to survive? With expanding urbanization, the problems held by those bat species in the minority will only spread and expand their struggles with survival. To properly ensure the protection of all bat species in an area some ponds may need to be specialized to favor certain species over those who have more generalized needs.
While the essay could always be improved by adding more variables to future studies, the authors do a great job in addressing where there is lacking information and next steps that could be taken to improve further.
Reference
L. Ancillotto, L. Bosso, V.B. Salinas-Ramos, D. Russo, The importance of ponds for the conservation of bats in urban landscapes, Landscape and Urban Planning, Volume 190, 2019, 103607, ISSN 0169-2046,
https://doi.org/10.1016/j.landurbplan.2019.103607.