Introduction


Bats are unique and important organisms. They play a vital role in the correct function of
ecosystems and that is why it is necessary to ensure the conservation of their species. Besides
insectivorous bats being the primary consumers of nocturnal insects, as bioindicators, bats are
particularly sensitive to various alterations in their habitats, such as a change in their food
sources or changes in temperature, likely caused by global warming (Ancilotto et al. 2016). They
are also sensitive to the spread and major change of their occupied area or rise of sea levels,
submerging some cave roosts under water (McWilliam, 1982). Pollution caused by heavy metals as a
result of urbanisation is evidenced by the presence of metals such as cadmium or lead in some bats
(O’Shea & Johnson 2009) and a study (Vaughan et al. 1996) has shown that polluted waters can have a
negative effect on bat activity, attesting that bats can be used as bioindicators of water quality.
This sensitivity to a vast amount of changes serves as warning and proof to various parties
studying ecological changes to the environment. Even though there are many different organisms that
act as bioindicators, bats have a particularly high significance thanks to their wide geographic
range, their slow reproductive rate (their population size may drop quickly), their taxonomy being
relatively stable and their responses to environmental changes correlating with those of other
indicators (Jones et al. 2009).

Insectivorous species of bats play a critical part in lowering the negative effect of agricultural
insect pests on crops and fruit orchards (Bartonička et al. 2017). By hunting and consuming
agricultural pests such as June bugs, cucumber beetles, cotton bollworm moths, corn earworm moths,
tobacco budworm moths and Jerusalem crickets (Whitaker 1995), they not only lower their numbers,
but also help minimise the negative economic consequences that are brought on a country by crop
disease.  It is estimated that nowadays the economic value of bats, in regard to the aforementioned
issue, may reach up to 3,7 billion American dollars annually (Boyles et al. 2011).

Some tropical species of bats, known as plant-visiting bats, are important pollinators and plant
seed dispersers of many different plants, including primary cacti species in the Sonoran desert
(Molina-Freaner et al. 2004) or large seed fruits on various oceanic islands, where they are the
sole pollinators capable of performing this task (Fleming & Racey 2009).

The above reasons alone should ensure a high interest in bat conservation around the world. And
yet, most bat species are considered to be endangered (eg. Racey & Entwistle, 2003), with their
numbers decreasing into dangerous territory. With various laws in place to ensure their safety and
the sustainability of their populations, one would expect the species to thrive and yet, that is
not the case. The reasons that may contribute to this issue seem never-ending, but one that
particularly stands out, and that is the topic of this thesis, is the problem of motorways,
frequently used by vehicles of various sizes and the negative effects these roads have on bats. The
permeability of road constructions for bats is a topic that lacks research data, which may then
complicate the efforts to optimise safety measures placed to minimise the negative effects of roads
on our studied species.

Motorways are an unmistakable feature of every developed country and their expansions are not a
rarity. Road construction brings forth several negative effects that may influence the behaviour of
bats. The issues include noise pollution, which may result in a lower effectiveness during hunting
(Schaub et al. 2008), light pollution from the large lighting equipment used during evening
construction, which may cause bats to abandon their regular flight corridors or hunting grounds
(eg. Rydell 1992; Blake et al. 1994), and disturbance of existing roosts and their possible
relocation (Altringham & Kerth, 2016) caused by the removal of vegetation and old buildings near a
construction site of a road. Once the new road is built, the mentioned effects continue, and new
ones appear. Roads may serve as barriers between roosting sites and foraging ground (Altringham,
2008) due to the reluctance of certain species of bats to cross these structures. They also cause
fragmentation of a habitat and may cause habitat loss. Roads may pose as a threat to certain bat
populations due to direct collisions of vehicles with individual foraging or migrating bats
(Geisler et al. 2009).

Bat hunting strategies vary from one species to another. That results in different flight heights
between clutter-adapted, edge-adapted, and open-adapted species (Abbott et al. 2011), which in turn
may result in various and unequal risks of collision with vehicles when commuting across roads and
road structures. Due to the risk of collisions, various mitigation measures and constructions have
been implemented to reduce the possible dangers.

 It is possible to determine the probability of a bat flying either above or under a road
construction such as a bridge using information on flight heights. However, we must take into
consideration the fact that behaviour in regard to flight height and hunting strategies may change
due to the natural unpredictability of animal behaviour (CEDR, 2016a). That is why scientific
observation of the permeability of road structures is needed.

The aim of this thesis is to describe in more detail the possible effects of motorways on bats,
using information from various existing studies; to summarise the mitigation measures that are put
into place, in the hopes of reducing bat mortality caused by direct collisions with vehicles; to
review the effectiveness of these measures by the means of existing studies; to sum up different
bat hunting strategies used among species most commonly found in the area of our study, South
Moravia; and to scientifically determine which species of bats are more likely to fly above a
bridge standing in their flight path and which prefer to fly below it, using monitoring equipment
in the field and then processing the results, in the hopes of contributing with useful data to the
efforts of improving safety measures in position to protect bats.