The ecology of seed dispersal by small rodents: a role for predator and conspecific scents

Abstract

Summary1. Seed-caching rodents play a key role in the ecology of seed dispersal by not only consuming but also dispersing seeds. Rodent foraging behaviour is usually framed within optimal models, which predict that their decisions should maximize food intake and minimize foraging costs. Although predation risk and seed pilferage by conspecifics have been envisaged as two potential costs, their relevance for seed-caching behaviour and seed dispersal has barely been addressed. 2. To test the effect of predation and pilferage risk on the patterns of seed predation/dispersal by rodents, we performed a field experiment using a tri-trophic-level model (plant-mice-carnivore; Quercus spp-Apodemus sylvaticus-Genetta genetta) and the scents of the predator and conspecifics as direct cues. The behaviour of mice was analysed with video cameras set for continuous recording on consecutive nights, and we used tagged acorns to assess the patterns of acorn predation and dispersal. 3. Our results revealed that rodents were able to discriminate between the scents of genet and conspecifics and modified their seed dispersal behaviour accordingly. Mice spent more time 'sniffing' in rodent cages than in genet cages, where they displayed more 'vigilance and freezing' behaviours. In sites with mice scents, acorns were dispersed at shorter distances and were less predated. Conversely, in sites with genet scents acorn removal was delayed. 4. These results show that chemosensory information on predators and conspecifics influences the foraging decisions of seed-caching rodents over short spatial and temporal scales. This might entail cascading effects on the regeneration of plants. In sites where rodents perceive the risk of predation, inefficient foraging behaviour may result in less successful seed dispersal. Conversely, the detection of conspecific scents may increase dispersal efficiency and seedling recruitment. 5. Ultimately, the relationships between two distant levels in trophic webs (plants-carnivores) appear intricate, since carnivores may affect seed dispersal by changing the foraging behaviour of their prey (the seed disperser). This indirect relationship should be considered as a new dimension of the ecology of seed dispersal by small rodents.

Defaunation and fragmentation erode small mammal diversity dimensions in tropical forests

“…Indeed, large rodents from Caviidae and Echimyidae and marsupials from Caluromys genus were the first groups to disappear in the presence of anthropogenic pressure, such as fragmentation and defaunation (Chiarello 1999, Costa et al 2005. Knowing that biodiversity loss is not a random process (Dirzo et al 2014), even for small mammals, there are biased impacts on these species that influence important functions such as seed dispersal and predation (Vieira et al 2003, 2006, Sunyer et al 2013), controlling the seeds reservoir of the forests, as well as in the dispersal of mycorrhizal fungi (Janos andSahley 1995, Mangan andAdler 2002). Phylogenetic and functional diversity are often loosely correlated (Pavoine et al 2013) and has been reported in birds (Trindade et al 2012, Sobral andCianciaruso 2016), large mammals (Safi et al 2011), fish (Cachera and Le Loc'h 2017) and plants (Flynn et al 2011).…”

Synzoochory: the ecological and evolutionary relevance of a dual interaction

“…This phenomenon occurs for example when jays or tree squirrels pilfer and redistribute primary caches made by conspecifics (Vander Wall, , 2002b; Emery & Clayton, ). In fact, intraspecific cache pilfering is not rare among scatter‐hoarding rodents and corvids (Vander Wall, , 2002b; Gerhardt, ), and may have influenced the foraging and caching behaviour of the dispersers and the spatial pattern and dispersal distance of cached seeds (Moore et al ., ; Sunyer et al ., ). Consequently, we presume that many nut‐bearing trees are frequently dispersed both primarily and secondarily by the same species of rodents and birds.…”

The ecological significance of secondary seed dispersal by carnivores

“…Carnivores can also have indirect effects on seed dispersal when seed dispersal behavior of the primary disperser (or seed predator) is altered by carnivore presence (Sunyer et al. , Steele et al. ).…”