Summary
Lactation is a process associated with mammals, yet a number of birds feed their newly hatched young on secretions analogous to the milk of mammals. These secretions are produced from various sections (crop organ, oesophageal lining and proventriculus) of the upper digestive tract and possess similar levels of fat and protein, as well as added carotenoids, antibodies and, in the case of pigeons and doves, epidermal growth factor. Parental care in avian species has been proposed to originate from dinosaurs. This study examines the possibility that some dinosaurs used secretory feeding to increase the rate of growth of their young, estimated to be similar to that of present day birds and mammals. Dinosaur ‘lactation’ could also have facilitated immune responses as well as extending parental protection as a result of feeding newly hatched young in nest environments. While the arguments for dinosaur lactation are somewhat generic, a case study for lactation in herbivorous site-nesting dinosaurs is presented. It is proposes that secretory feeding could have been used to bridge the gap between hatching and establishment of the normal diet in some dinosaurs.
Key words: nesting, parenting, crop milk, crop, birds, mammals
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Simply titled “Dinosaur lactation?”, the commentary by University of Wollongong health scientist Paul Else speculates that a peculiar form of nurturing seen among modern birds might have originated among non-avian dinosaurs. Birds such as doves, flamingos, penguins, and petrels can produce a milky substance in their crops or other parts of their upper digestive system. The fluid contains antibodies, fat, protein, and other nourishing elements. Perhaps, Else speculates, non-avian dinosaurs fed their young a similar substance.
There is no direct evidence that dinosaurs produced “crop milk.” Else makes his case based upon the evolutionary connection between birds and dinosaurs, as well as the hypothesis that the substance would have been one way for adult dinosaurs to feed their newly-hatched young. Of all dinosaurs, Else suggests that hadrosaurs such as Maiasaura (pictured above) were the most likely to produce milk because their babies may not have been able to effectively break down plant food until they developed teeth and the proper gut flora…
Maiasaura Milk? http://on.natgeo.com/X11wRw via @NatGeoMag
Else, P. 2013. Dinosaur lactation? Journal of Experimental Biology. 216: 347-351. doi: 10.1242/jeb.065383
