By Ella Davies

Earth News reporter

Please turn on JavaScript. Media requires JavaScript to play. Advertisement Unique hedgehog-like mammals have been filmed using their quills to communicate. A BBC film crew captured footage of the streaked tenrecs in the eastern rainforests of Madagascar. By rubbing together specialised quills on their backs, the tenrecs made high pitch ultrasound calls to each other in the forest undergrowth. The footage is the first of a mammal communicating in this way, a technique called "stridulation".

Watch more video clips of tenrecs The lowland streaked tenrec (Hemicentetes semispinosus) resembles both a hedgehog and a shrew with black and yellow stripes, and is found only in Madagascar. A film crew hoping to feature these visually striking animals in the BBC series Madagascar faced a number of challenges. As eaters of invertebrates, particularly earthworms, the best time of year to film the tenrecs was the rainy season. The time of day also played a considerable role. "They're active during the day and during the night but they hide a lot so it can be difficult," said local conservation expert Dr Rainer Dolch who assisted the crew in their search. Despite being crepuscular and used to twilight conditions, the streaked tenrecs were unconcerned by the crew's lights as they foraged on the forest floor. However, recording the sounds the animals made required more sophisticated technology. Most of the sounds are too high for us to hear so we took a bat detector so that we could also pick up ultrasonic noises

Researcher Emma Napper Streaked tenrecs are known to communicate using high-pitch tongue clicks when foraging but many of the sounds are beyond human hearing. "Most of the sounds are too high for us to hear so we took a bat detector so that we could also pick up ultrasonic noises," said researcher Emma Napper. Using the bat detector, the filmmakers found that the seemingly "quiet" mammals were constantly communicating. Scientists have theorised that tenrecs could also be using high pitched calls to echolocate in the dark forest, finding their way with sound rather than sight in a similar way to bats. The film crew were also hoping to record evidence of a particularly bizarre audio behaviour, unique to streaked tenrecs. In the 1960s, streaked tenrecs were found to communicate using specialised quills on their backs, rubbing them together to make high pitch ultrasound calls. The tenrec's pale 'stridulating' quills are very different to those found on the rest of its body.

Animals such as crickets, beetles and vipers are known to communicate by rubbing together body parts in behaviour known as "stridulation". However, stridulation had never been filmed before in mammals. The crew captured footage of the tenrecs rubbing together these specialist quills on their back as they foraged. Few studies have been made to investigate why streaked tenrecs communicate both vocally and via their quills but they are currently the only mammals known to do so. TENREC FACTS Streaked tenrecs raise their crown of spines when threatened Their main defence is thrusting these detachable spines into predators Common predators of tenrecs include Malagasy civets, fossas and mongooses Tenrecs are a diverse family of mammals that resemble shrews, mice and even otters. There are approximately 30 species in Madagascar including the rare web-footed aquatic tenrec (Limnogale mergulus) and the spiny, rabbit-sized common tenrec (Tenrec ecaudatus). The rich diversity of tenrecs on Madagascar is explained by scientists as evidence of the Darwinian theory of "adaptive radiation". They propose that the tenrecs evolved from a single ancestor 60 million years ago, possibly a mammal that floated across the sea from mainland Africa. With no other mammals on the island at the time, the different species of tenrecs are thought to have evolved into a diverse family as they adapted to Madagascar's wide variety of environments, free from competition. Madagascar continues on BBC TWO at 2000 GMT on Wednesday, February 16.



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