There are many behaviors that persist throughout many different species and across long periods of time. These behaviors serve important roles in surviving different environments and communicating different information between individuals involved. One such behavior is the care and attention that is given to young of species.
Species use tremendous energy to ensure that these successive generations survive until they are ready to be on their own. Another behavior is mating, which is important to reproduce and produce new generations to carry your genes into the future. Of interest here is the behavior of communal roosting. Communal roosting is a behavior where individuals from the same species form groups in response to certain types of environmental signal. The individuals will gather at an area for some period of time to deal with the signal and continue to do so whenever the signal reappears.
The types of signals that are responded to range from the dark, which can be filled with predators, to rainfall. There are costs to any behaviors, including roosting. When animals are in communal roosts, they are most exposed and cannot hide as easily as single individuals from predators. However, their number does aide in their defense. Large communal groups also need large amounts of food to sustain their numbers, which can also be a problem where food is becoming scarce. Roosting is not a new behavior and new research is showing exactly how old it may be.
There are many species that roost from insects to humans. The Red-billed Quelea have roosts that are composed of over 10 million individuals that cause trouble in different parts of Africa because of their numbers. The pigeons that are making their homes in every crevice of your house and around any buildings they can find are engaging in communal roosting. Even humans engage in some communal roosting. Our ancestors probably roosted together to protect each other from the darkness that surrounded them, which had numerous predators.
Nowadays, we roost because we enjoy snuggling with someone we love. In extreme cases, we try to roost together to conserve heat and stay warm in cold environments. One of the most common reasons for roosting surrounds the darkness. When humans are scared of the dark, they go to other humans to seek out comfort and safety. When we are with other people, the darkness seems less threatening and easier to manage. Some birds roost to stay warm or safe while others might roost to ensure they get a steady food source. Insects like the red postman butterfly also engage in communal roosts. Researchers believe that these butterflies roost together to deter predators from attacking them at night simply because the predators prefer to attack single butterflies instead of groups.
Recently, researchers have uncovered fossils of dinosaurs that seem to indicate signs of communal roosting, a behavior that was not seen in dinosaurs before. The fossils were of three dinosaurs that were taken by poachers. The fossils were apprehended by Mongolian customs in 2006 and vertebrate paleontologist Greg Funston, of the University of Alberta in Canada, led the team that would analyze the fossil. Using geochemical analysis, the researchers found that the fossils were over 70 million years old and were from the Cretaceous Period, which ranged from 145 million to 60 million years ago.
The three dinosaurs in the fossil were found to be a new species of oviraptorid, which were a bird-like group that walked on two legs with toothless beaks and long necks. Of the three specimens, two were positioned like emus or ostriches when they engage in deep sleep. They were huddled close together tightly and gave clear indications of communal roosting behavior.
Most fossil records of dinosaurs engaging in sleep behavior have always been single dinosaurs rather than pairs or more. The researcher’s estimates, based on weight and bone development, that the fossils were of young dinosaurs. Given the communal roosting and the similar age, they estimate that they were probably siblings or closely related. The same can be probably be said of the third specimen, which was more fragmented and not easy to measure as the other two.
The researchers believe that the animals were roosting together to conserve heat and stay warm in the cold nights. Funston surmises that sandstorms or frigid weather may have driven the animals to seek out each other for warmth to stay alive. This analysis does face some resistance from other researchers because most animals that roost for warmth are usually smaller than these oviraptorids, which are around the size of german shepherds. Some scientists suggest that they may have been roosting because of hazardous conditions or simply because of convenience rather than behavior. It is certain that they sleep together at least because they died in that same position. If they were awake, whatever killed them, would have caused panic and there would be indications of escape attempts.
These represent the first and only case of dinosaurs engaging in communal roosting, so there is much more work needed and evidence to support this new behavior in dinosaurs. It could have been a fluke of behavior or it could have been the social nature of these species. To gain a more accurate idea of this, we need more fossils that showcase similar behavior in order to build a substantial sample size, like any other research that focuses on animal behavior.
These sorts of research are an important connection between the modern and the ancient because there is so much information that was lost between extinction events. Understanding how old behaviors work and relate to modern behaviors help us to understand more about the evolution of those behaviors, species, and ourselves. There are many other areas we see this happening such as instances of photosynthesis, raising our young, or reproducing. As we get more fossils and information about the ancient world, we will be able to build more accurate and precise records that examines the development of life on Earth.