Allometric scaling of seed retention time in seed dispersers and its application to estimation of seed dispersal potentials of theropod dinosaurs

Abstract

Seed retention time (SRT), the time interval between seed ingestion and defaecation, is a critical parameter that determines the spatial pattern of seed dispersal created by an animal, and is therefore, an essential component of trait‐based modelling of seed dispersal functions. However, no simple predictive model of SRT for any given animal exists. We explored the linkage between animal traits and SRT. We collected previously published data on mean SRT for 112 species of birds, mammals, reptiles and fishes and investigated the general allometric scaling of mean SRT with body mass for each taxon. Moreover, we analysed the effects of food habit and digestive strategy on mean SRT for birds and mammals. In general, mean SRT increased with body mass in all four taxa, whereas the pattern of allometric scaling varied greatly among the taxa. Birds had a smaller intercept and larger slope than those of mammals, whereas reptiles had a much larger intercept and smaller slope than those of either birds or mammals. For birds, food habit was also detected as an important factor affecting SRT. We applied the allometric scaling that was obtained for birds to estimate mean SRT of extinct Mesozoic dinosaurs (Theropoda) – few of which are assumed to have acted as seed dispersers. SRT for large carnivorous theropods was estimated to be 4–5 days, when considering only body mass. The present study provides allometric scaling parameters of mean SRT for a variety of seed‐dispersing animals, and highlights large variations in scaling among taxa. The allometric scaling obtained could be a critical component of further trait‐based modelling of seed dispersal functions. Further, the potential and limitations of the scaling of animal SRT with body mass and a future pathway to the development of trait‐based modelling are discussed.

Body mass and skull dimensions predict seed dispersal capacity in bats, primates and carnivores from tropical forests

“…In addition, evidence shows that body size can be used as a strong indicator of seed retention time of extinct animals. This is suggested by a study using body mass of extinct Mesozoic dinosaurs to deduce their seed retention times that determines the spatial pattern of seed dispersal (Yoshikawa et al 2019). The strong covariations that we observed, indicate that seed size ingested, retention times and seed dispersal distance could be inferred in extinct animals based on morphological measurements.…”

Community‐wide seed dispersal distances peak at low levels of specialisation in size‐structured networks

“…Importantly, functional traits can also describe the ecological processes and functions that result from species interactions. For example, frugivore body size scales with gut passage time and movement distance, which means that large frugivores retain seeds longer and could carry them over greater distances than small frugivores (Robbins 1993, Yoshikawa et al 2019). This results in longer‐distance seed dispersal for plant species dispersed by large frugivores (Jordano et al 2007, Wotton and Kelly 2012, Costa‐Pereira et al 2018).…”

The importance of individual movement and feeding behaviour for long-distance seed dispersal by red deer: a data-driven model

“…Ungulates form a large and important group in this regard since they are often the dominant herbivores in a landscape [ 12 ], disperse seeds of a variety of plant species [ 12 , 13 ] and often disperse a large number of seeds (high seed load) [ 13 , 15 , 22 ]. Furthermore, the well documented allometric relationship of body size to gut retention time and movement velocity makes large animals likely effective vectors for LDD [ 12 , 22 , 23 ]. Research into ungulate mediated zoochory has mostly focussed on extrinsic determinants of seed dispersal.…”

“…We parameterize the general mechanistic dispersal model for individual deer and different plant species by combining individual-specific distributions of displacement distance ( d ) that were determined for GPS-tracked deer, with a distribution of seed passage times ( p ) modelled using experimental data for red deer [ 23 ]. We also quantify seed load (Q) from dung collections targeted at the GPS-tracked individuals and a subsequent greenhouse seedling emergence experiment.…”