Lay, brood, repeat: nest reuse and site fidelity in ecologic time for two Cretaceous troodontid dinosaurs

Abstract

Whereas 'biological site fidelity' refers to the regular reuse of a favored locale (e.g., breeding ground or nest) by an individual animal, 'paleontological site fidelity' typically refers to repeated use of a nesting locality by a herd or species over geologic time scales. Two new Cretaceous specimens from the Two Medicine Formation of Montana, U.S.A., and the Liantoutang Formation of Zhejiang, China, each preserve two closely superimposed clutches of the egg form Prismatoolithus. These eggs belong to the Troodontidae, small theropod dinosaurs sharing a close ancestry with Aves. In both specimens, eggs of a lower clutch are truncated at a level below what would normally preserve in an undisturbed hatched clutch. These traces differ from past examples of dinosaur site fidelity in (1) the close or cross-cutting relationship of the clutches, (2) the precise overlay of clutch atop clutch, and (3) the implication of nest reuse and, thus, site fidelity on an ecologic rather than geologic scale and at approximately the individual rather than species level. Given the likely extended occupation of troodontid nesting sites by attending adults, factors such as nesting success and territoriality may, in addition to favorable substrates, have influenced the behaviors recorded by these specimens. The arrangements of eggs as clutches within the geologic record represent trace fossils. Thus, they record past in situ behavior, providing important insight into dinosaur nesting. In addition, they can serve as independent indicators of substrate conditions and sedimentary history, potentially refining our understanding of paleoenvironments.

The first record of dinosaur eggshell from the Horseshoe Canyon Formation (Maastrichtian) of Alberta, Canada

“…The combination of teeth and eggshell suggests that FTS-2 represents a nesting site of Albertavenator curriei. Were this the case, the inference of prolonged deposition at the site would support previous hypotheses of nest-site fidelity (Varricchio et al 2015). As suggested by Ryan et al (1998), perinate material from other dinosaur taxa at FTS-2 and L2000 might be explained by targeted predation by Albertavenator curriei.…”

Information thresholds, habitat loss and population persistence in breeding birds

“…In ecological time, fidelity and prospecting can strengthen the correlation between occupancy and site quality. Site fidelity is one of the first patterns and mechanisms of non‐random habitat use to be described in the avian literature (Hinde ), and the mechanism itself appears to date back at least as far as the Cretaceous in Troodontid dinosaurs (Varricchio et al ). Prospecting for social information on conspecific performance (Boulinier and Danchin , Reed et al , Betts et al ) accentuates the above relationships, with diminishing returns from an increase in the number of prospecting events (Fig.…”

Pain in dinosaurs: what is the evidence?

“…The proximity of adults able to protect injured young is a necessity; the nesting behaviour of some dinosaurs is compatible with this [43,68]. Some buried eggs in supervised mounds, as do crocodilians and some birds.…”