Terrible Lizards, Feather Heads, and Awesome Dads!
by. Dr. Aaron Pan, Executive Director, Don Harrington Discovery Center
Theropods, the “beast feet” dinosaurs, include some of the most vicious and terrifying prehistoric organisms we know about. We can recognize them by their impressive names like Tyrannosaurus, Allosaurus, Spinosaurus, and Velociraptor, and their even more impressive sharp teeth, powerful jaws, and lethal claws. However, they also include some of the most beautiful, lyrical, and good parenting animals today, because Aves, more commonly known as birds, are also a group theropod dinosaurs!
This Father’s Day we want to wish a wonderful day to all the dads out there and introduce you to some pretty cool dinosaur fathers as well. But why discuss bird and other theropod dinosaur and not mammal fathers? Well, birds are quite rare in the natural world in that biparental care (care of young by both parent animals) occurs within 90% of all living bird species (Wesołowski, 2003). Only a paltry 5-7% of mammal species have both parents contributing to the care of their offspring.
The Grey Hornbills (Ocyceros species) are amazing birds that live in India and Sri Lanka. The birds are cavity nesters and usually nest in the same tree cavity year after year. The female, when she is ready to lay her eggs, settles into the cavity and begins to seal most of the entrance closed using her bird dropping and mud pellets brought by the male. The barricaded entrance is an adaptation to protect the eggs/hatchings and mother from predators. Once the large entrance becomes a small slit, it becomes the dutiful father‘s job to provide food for the sheltered family. He makes several food trips a day for 2 to 3 months straight until the hatchlings are large enough to leave the cavity nest.
Great Horned Owl (Bubo virginianus) dads also provide food for their family (female and young) as well, but the considerable amount of food and meal sorties necessary to do this is only fully realized when you note that most of the “peckish” (sorry, I had to..) family members each individually outweigh him (the female by 25% and at some points in their growth, the young as well).
The Red Phalarope (Phalaropus fulicarius), a widespread water bird, is also a very devoted father. After the female lays four eggs in a nest she disappears, often to find a second mate. The male, however, incubates the eggs and raises the hatchlings on his own.
Did you know that there is also evidence of good dinosaur fathers in the fossil record? Nests of some species of oviraptor (a group of parrot-like beaked theropods from Asia) and troodontids (a group of small, bird-like dinosaurs) provide evidence of clutch brooding by adult male dinosaurs (at least within these two groups). Fossil individuals of the prehistoric daddies are identified as male due to their lack of medullary bone (Varricchio et al., 2008). Medullary bone is a special type of irregular bone tissue in female birds and non-avian, theropod dinosaurs. The tissue acts as a reservoir for calcium and phosphorus that is absorbed by the body during eggshell production (Dacke et al., 1993; Varricchio et al., 2008). Males, which do not produce eggs, lack medullary bone tissue. Since the adult individuals found at the fossil sites lack this tissue, they can be identified as males. In addition, large egg clutch sizes, which both oviraptors and troodontids produce, are often indicative of parenting systems where males provide extensive parental care (Varricchio et al, 2008). This can be observed today in both ostriches and emus (Varricchio et al., 2008).
Happy Father’s Day (to those that are feathered or furry)!
Dacke CG, Arkle S, Cook DJ, Wormstone IM, Jones S, Zaidi M, Bascal ZA. 1993. Medullary bone and avian calcium regulation. Journal of Experimental Biology 184: 63-88.
Varricchio DJ, Moore JR, Erickson GM, Norell MA, Jackson FD, Borkowski JJ. 2008. Avian parental care had dinosaur origin. Science 322: 1826 – 1828.
Wesołowski T. 2003. The origin of parental care in birds: a reassessment. Behavioral Ecology 15. 520-523.