YDT 2023 Soru=34

According to the passage, other than tracking transmitters, ----.

In the 1900s, birds were tagged with string around their
legs and handwritten identification codes. In the 1940s,
radar was used to study migrating animals, and by the
1950s, sonar was being used. In the last 30 years,
scientists have started to track animals using satellite
technology. In recent years, tracking transmitters have
become smaller and more efficient thanks to
improvements in battery technology and the use of solar
panels. Generally, 3% of the weight of an animal is
considered to be the upper limit for the weight of such
devices, and so far, the lightest transmitters to be
developed weigh only 0.6g. Indirect techniques are used
too. For example, Australian researchers use ‘proximity
sensors’ that emit a beam of electromagnetic radiation
to monitor bats without the need for physical contact.
These are used to model and assess the spread of
diseases. Other non-invasive methods include:
temperature and CO2 level checks, monitoring inside
beehives, counting footprints next to ant nests, using
drones to collect periodic photos of animals, and
positioning cameras next to nests and hives for use with
image recognition software to count individual animals.