Wild Chimps Prefer a Firm Bed	Chimpanzees are quite choosy when it comes to their sleeping arrangements and new research suggests the apes prefer a firm bed made from stiff resilient wood.	Like humans chimpanzees depend on a good night's sleep to function well the next day but chimps don't tuck themselves into the same bed each night. Instead the primates build a new nest each evening from scratch. High up in the forest canopy the animals interlace strong stems and foliage into a basketweave creating a thick springy mattress that sinks in the middle.	Scientists have known that chimpanzees build these sleeping platforms since Jane Goodall famously studied the apes in Tanzania's Gombe Stream National Park in the 1960s. There seem to be several advantages to snoozing high off the forest floor. In 2011 one intrepid Cambridge researcher who slept in wild chimpanzee nests for six nights  reported that the nests kept her warm and relatively free of bug bites; they also eased her worries about the hyenas she heard calling in the night. [Sleep Soundly: Images of Primate Nests]    	And now another group of researchers has looked at whether chimpanzees are picky about the type of wood they use for their nests. Anthropologists David Samson of the University of Nevada Las Vegas and Kevin Hunt of Indiana University in Bloomington  examined 1844 chimpanzee nests in western Uganda's Toro-Semliki Wildlife Reserve.  	They found that 73.6 percent of the nests were built with the plant species  Cynometra alexandri despite the fact that this tree was hardly the most common species in the area representing just 9.6 percent of the local arboreal population.	C. alexandri  is known locally as ironwood because it is dense and resilient  properties that make it a popular construction material. Those same qualities seem to attract sleepy chimpanzees the researchers wrote in their report published April 16 in the journal PLOS ONE.	Samson and Hunt's tests proved that C. alexandri  was not only the stiffest but also had the greatest bending strength of the seven trees most commonly used by the apes.	Ugandan ironwood may have other advantages too. With its small densely packed leaves branches of the tree may be more insulating and more comfortable to sleep on than the branches of other local tree species which can have sparse protruding stems.	Ugandan ironwood might even keep bugs at bay. In a study published last year in the journal Primates Samson and Hunt found that mosquitos were less likely to congregate around C. alexandri which is thought to have repellant properties.  	The results suggest that chimpanzees might consider several physical traits of trees when choosing their bedding including stiffness strength and leaf surface area and that they select species that provide the widest range of advantages including predator avoidance postural stability thermoregulation and pathogen avoidance the authors wrote.	Follow Megan Gannon on  Twitter  and  Google+.  Follow us @livescience  Facebook &  Google+. Original article on  Live Science.