For those who’ve ever wondered whether ‘tagging’ is a humane way of treating our animal friends, here’s some food for thought. Scientists have found that tags fitted to fish in order to chart their progress and survival can often alert nearby predators to their presence. Scientists have called the phenomenon the ‘dinner bell effect’.
British researchers published their findings in the journal Proceedings of the Royal Society B, findings which suggest that tagging may alert superior predator species to the existence of tagged populations. The scientists conducted extensive tests with captive grey seals; eventually, they found that the subjects qucikyl began to associate the sound with an easy meal.
The experiment placed ten seals in a concrete pool divided up into twenty boxed sections. Tagged and untagged fish were then released into the boxes randomly. “The seals found the tagged fish in fewer box visits than the untagged fish in later trials, demonstrating the learned use of the acoustic tag to locate food,” the report stated, effectively proving the ‘dinner bell effect’.
Over time, it seemed as though the seals were adapting to the new information and finding the fish at a much faster rate. Scientists chalked this up to the slight sounds being emitted by the tags, a factor which had previously been ignored.
‘Acoustic tags’ are a technology used in what are widely known as ‘mark-and-recapture’ studies. The technology utilises ultrasonic frequencies in order to feed data back to the observing scientists. Though scientists previously believed the sounds to be imperceptible to various undersea life, the British team says that theory can now be discounted.
“Our results… illustrate the importance of considering the auditory sensitivities of all animals in the environment when designing an acoustic tagging study. We showed that acoustic tags… aid prey detection, potentially increasing predation of tagged animals and potentially skewing study findings”.
The report concludes that researchers and scientists must exercise more caution when interacting with a delicate balance: “When introducing artificial sound sources into an environment, it is important to take into consideration all potential effects on local species, both detrimental and beneficial.”
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