By Stephen Beech

Narwhals have been caught on camera colliding with deep ocean monitors.

The mysterious toothed whale species native to the Arctic has been involved in "hundreds" of incidents with underwater recording devices.

The narwhals may be mistaking the recording equipment for cod they love to feed on, say scientists.

Underwater passive acoustic recording is vital for researchers to monitor and study marine animals in their natural environment with minimal disturbance.

But the latest findings, published in the journal Communications Biology , suggest passive monitoring is not as non-invasive as previously assumed.

Research leader Associate Professor Evgeny Podolskiy said: "Using passive acoustic monitoring to detect acoustically active animals helps to census biodiversity,

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