Fruit colour and edge effects poorly explains frugivorous bird-plant interactions in disturbed semideciduous forests

Fruit colour is considered an important feature mediating interactions between plants and frugivorous birds. Despite that, colour mediated interactions are context-dependent, and habitat disturbances may affect how frugivorous birds perceive fruit colours. This study assessed the influence of fruit colour and edge effect on the consumption of artificial fruits by frugivorous birds in three disturbed semideciduous forests in southeastern Brazil. In each of those areas, we performed a field experiment in which we placed artificial fruits of three different colours on plants and recorded their consumption by birds. Red-coloured fruits were ingested more often than yellow, but neither of them was consumed differently from dark-blue. Edge effect only affected consumption of yellow fruits. Our data neither support the hypothesis of preferential consumption of the highest contrasting colours nor of increased fruit consumption in the forest interior. These findings indicate that colour and edge effects, as well as the interaction between them, may not be strong predictors of fruit choice by birds in disturbed environments, especially because generalist species, which are less sensitive to the physical alterations in forests, are favoured in these areas.

Differential fruit choice in two simpatric monkey species and frugivorous bats in southern Mexico

Con el objetivo de examinar el papel que juegan las especies vegetales como fuentes alimenticias en la selección de frutos de agentes dispersores (Alouatta pigra, Ateles geoffroyi y murciélagos frugívoros), se realizó un estudio en selvas secas en el sureste de Yucatán, México. Se registraron los frutos consumidos por murciélagos usando colectores y, en el caso de los monos, se implementó el método de animal focal. El número de frutos consumidos registrados para ambas especies de primates y murciélagos fueron 342 y 386, respectivamente. Se determinó que los murciélagos depositaron frutos con pequeñas cantidades de pulpa, mientras que los monos contribuyeron mayormente con frutos totalmente despulpados (contrastes por pares LSD p < 0.05). Entre la variedad de especies de frutos en la dieta de los primates se detectó que A. pigra eligió frutos de las especies menos abundantes como Enterolobium cyclocarpum Jacq. Griseb. (1860) en vez de aquellas más abundantes (Manilkara zapota (L.) P. Royen (1953) y Brosimum alicastrum Sw. subsp. alicastrum C.C. Berg (1972)). El tipo de manejo de frutos y semillas causado por los primates sería más beneficioso para la germinación de las semillas que los aplicados por los murciélagos. Además, esta elección y manejo del fruto podría depender de sus características y la disponibilidad espacio-temporal de las especies de plantas como fuente de alimento.

Olfaction in the fruit-eating bats Artibeus lituratus and Carollia perspicillata: an experimental analysis

ABSTRACT Studies suggest that frugivorous bats search and select fruit mainly by olfaction so that they can be attracted by smell alone. The aim of this study was to evaluate, in captivity, the behavioural response (number of foraging attempts) of Artibeus lituratus and Carollia perspicillata offered essential oils extracted from ripe fruit of Ficus insipida (Moraceae) and Piper hispidum (Piperaceae) as well as intact fruit wrapped in gauze to attract bats with reduced visual stimuli. Based on previous reports, we hypothesized that A.lituratus would exhibit preference for Ficus fruits/oil while C. perspicillata would prefer Piper fruit/oil. Four arrangements of these attractants were tested in triplicate: P. hispidum fruit vs. F. insipida fruit, P.hispidum oil vs. F. insipida oil, P. hispidum oil vs. F. insipida fruit and P. hispidum fruit vs. F. insipida oil. As expected, in all tests, A. lituratus showed the highest number of foraging attempts in F. insipida while C. perspicillata in those of P. hispidum. Based on the number of foraging attempts both species exhibited a positive response to their favorite fruit genera, though the differences were not always statistically significant. The results confirm the importance of smell in fruit choice by these species.

Disentangling factors controlling fruit and seed removal by rodents in temperate forests

Fleshy fruits fall on to the ground together with cleaned seeds previously ingested by primary dispersers, offering a wide range of fruits and seeds to the ground foragers. Although nutritional properties strongly differ between fruits and seeds, this different seed presentation (cleaned seeds versus seeds within the pulp) has not been addressed in seed removal studies. This study reports on the removal of fruits versus their seeds in five fleshy-fruited species in a temperate forest. We found that rodents removed most of the seeds and partially consumed most of the fruits, preferring seeds to fruits. Rodents bit the fruits to extract the seeds, leaving most of the pulp. We found a preference ranking for the seeds (Sorbus aucuparia>Ilex aquifolium>Sorbus aria>Rosa canina>Crataegus monogyna) but no preferences were found for the fruits, probably due to their similarities in pulp constituents. Seed and fruit choice were affected by chemical and physical properties and not by their size. The presence of alternative and preferred seeds (nuts) delayed the encounter of the fruits and seeds and diminished their removal rates. We found that higher rodent abundance is not necessarily associated with higher removal rates of fleshy fruits. Rodent abundance, fruit size and seed size are minor factors in the removal of fleshy fruits and their seeds. This study underlines that scatter-hoarding rodents are important removers of fleshy fruits and their seeds, producing a differential seed removal depending on the seed presentation (with or without pulp), the nutritional properties of the seeds (but not of the fruits) and the presence of alternative food.

Fruit of a contrasting colour is more detectable by frugivores

Determination of the factors that rule the preference of birds for certain fruits is fundamental to the understanding of the co-evolution of plants and their dispersers (Alves-Costa &amp; Lopes 2001). Plants might compete for dispersers, and the response of dispersers will differ according to the variety of fruits available in nature (Denslow &amp; Moermond 1982, Herrera 1981). Seed dispersal by birds is directly related to certain features of fruit, including colour, size, shape, abundance, nutritional value, habitat and distance between plants that are fruiting (Alves-Costa &amp; Lopes 2001, Galettiet al. 2003, Leveyet al. 1994, Murrayet al. 1993). To understand how birds integrate these features in terms of fruit choice is a complex and widely misunderstood problem (Leveyet al. 1994).