Phillipp Island – Australia

In this australian conservation center koalas can be approached by tourists walking on a boardwalk placed in their natural habitat, the canopy of eucalyptus trees. The absence of escape behaviour or signs of distress suggested that koalas were not disturbed by tourists. However, stress reactions can be hidden and only physiological parameters can sometimes reveal them. Scientists went on to test the heart rate response of koala in presence or absence of tourists.

Bio-logger composition

Electrocardiogram recorder

To monitor the heart rate there are heart rate loggers that function like polar watches for marathon runners. Such devices record the interval between what is defined as a heartbeat by the machine. Yet, muscle activity can sometimes be confused with heartbeat and most devices are not specifically calibrated for a given animal. Scientists used therefore an electrocardiogram recorder! Pros, each QRS complex is individually recorded and as such there is no mistake possible: the user can discard any signal which does not correspond to a heartbeat. Cons, it requires sampling frequency as high as 1000 points per second.

Capture and device attachment

Strong as a koala

Waving a red flag attached to a long pole above its head is the best way to bring the koala down the tree. Holding it on the ground requires strength though. Even a small 3-4 kg female can push up two australian rangers if she’s unhappy. Electrodes are the trickiest bits to attach to the animal. Rather than to glue them to the skin inserting a clipping needle (like a piercing) is much safer and the electrodes can thus be easily removed at the end of the
experiment, without damage to the koala. Here, three electrodes are placed on the back to the koala.

Data recording

Stress influence

Besides the presence or absence of tourists, many parameters can influence the heart rate of a koala! Its sex, age, weight, etc. As such, scientists try to remove as much confounding factors as possible by working only on females of similar age and weight and on the same days to avoid environmental factors. Needless to say that it drastically reduces the number of individuals on which to work. In addition, handling the koalas probably stressed them a bit, so a delay was imposed to the loggers to start recording only after several days had passed, allowing the koalas to come back to their normal heart rates.

Data recovery

Data cleaning up

After recovering the logger, data are downloaded onto a computer. And now the scientists enter the painful process of cleaning up the data. Engineers develop automated identification scripts that allow them to detect all events that look like a QRS in the signal recorded by the logger. But this does not mean that the job is over, as now the scientists have to check, often one by one that detected events are truly what they are after.

Data interpretation

Touristic impact

Once the cleaning is down, comes the choice of the parameters to compare. Average resting heart rates between the individuals that were in contact with tourists were always statistically higher than those of koalas without contact with tourists. In other words, there was a slight – but significant – greater energy consumed by koalas that were in contact with tourists.


Considering data

Bio-loggers have delivered their data, scientists have interpreted them as objectively as possible. And now? What to do with this? There is no need for drastic measures! Making sure there is a turnover and that koalas are not receiving visits of tourists every day could help. Supplementing the diet of the koalas to compensate for the extra energy could also be an option.