Introduction
Most trees and woody lianas in tropical forests depend on animals for seed dispersal (zoochory), with many trees producing fruits that are attractive to animals (Howe & Smallwood 1982; Jordano 2000; Buitrón-Jurado & Ramírez 2014; Howe 2014). Frugivores disperse seeds by consuming the fruit pulp and spitting out the seeds after cleaning them from their pulp (synzoochory) (Howe & Kerckhove 1981; Corlett & Lucas 1990; Lobova et al. 2009), or they ingest fruits whole and the seeds are found intact in their feces (endozoochory) (Shilton et al. 1999; Tobler et al. 2010; Beaune et al. 2013). According to the Janzen-Connell hypothesis, the deposition of seeds away from the parent tree could be advantageous for the plant because the establishment and the survivorship of seedlings is affected by negative density dependent processes such as intraspecific competition, herbivores or pathogens (Janzen 1970; Connell 1971; Bell et al.2006; Mangan et al. 2010; Swamy et al. 2011). When endozoochory occurs, seed dispersal distances mostly depend on the transit time of the seed in the digestive tract and the movement of the animal (Traveset et al. 2007). Large‐sized dispersers, like elephants for example, show long-distance movements and long gut retention times, thus generating a more diverse, long‐distance dispersal pattern than smaller dispersers (Jordano et al.  2007 ; Nathan et al. 2008; Campos-Arceiz & Blake 2011; Bueno et al. 2013; O′Farrill et al.  2013; González & Stevenson 2014; Fuzessy et al. 2017). Thus, body mass can be expected to be an important driver of seed dispersal distance.
The outcomes of interactions between plants and frugivores are influenced by both plant and animal traits (Dehling et al.  2016). Many traits of animals influence the quantity and quality of seed dispersal and consequently impact the seed‐dispersal effectiveness (Schupp et al. 2010; Beckman & Rogers 2013). Avian body mass determines energy requirements, affecting foraging behaviour and consequently may constrain the size of fruit that can be ingested (Jordano 2000; Kitamura et al.  2002). Moreover, bill size or wing morphology in birds influence fruit handling and manoeuvrability for fruit access (Dehling et al.  2016). Nevertheless, no studies have explored the link between body mass or skull dimensions with the size of ingested seeds in mammals. Yet, body size and gape limitations can be expected to be important drivers of these relationships as they are for birds (Lord 2004; Godínez‐Alvarez et al. 2020).
Here, we focus on mammals with a predominantly frugivorous diet across three orders: Chiroptera, Primates, and Carnivora. Frugivorous bats are represented by the Pteropodidae family of the Old World (Africa, Asia, Oceania) and Phyllostomidae of the New World (America). They are able to carry up to 1.5x their body mass in fruit (Mahandran et al. 2018) and some can ingest and defecate a large amount of small seeds (Lobovaet al. 2009). Frugivorous primates are represented by strepsirrhines, platyrrhines (New World monkeys) and catarrhines (Old World monkeys and apes). They constitute up to 25-40% of the biomass of frugivorous animals in tropical forests (Chapman 1995). These taxa show high interspecific variability in terms of seed treatment and therefore in seed dispersal efficiency (Lambert 1999; Gross-Camp & Kaplin 2011). Frugivorous carnivores are mainly represented by the Viverridae in the Old World and the Procyonidae in the New World. Viverrids represent the third largest group of frugivorous mammals in the Indo-Himalayan region (Kitamura et al. 2002). Even if they are much less studied than primates and bats, frugivorous carnivores are recognized as important dispersers (Alves Costa & Eterovick 2007; Zhou et al. 2008; Nakabayashi et al. 2016). They consume a wide variety of fruits of which they disperse a significant number of intact seeds (Alves Costa & Eterovick 2007; Chakravarthy & Ratnam 2015).
Using global data including Neotropics, Asia, Africa and Madagascar, we tested the following questions:
1. Do body mass and skull dimensions predict the size of ingested seeds and fruits? We expected a positive relationship between body mass and cranial dimensions with the size of consumed fruits and ingested seeds.
2. Do body mass and skull dimensions influence seed dispersal distance? We expect a positive relationship between body mass and seed dispersal distance in relation to digestion times, with longer transit times resulting in greater seed dispersal distances.