Caring for Pollinators - Bundesamt für Naturschutz

Tschapka Fact sheet pollinators: Bats (Chiroptera)
In the New World bat pollination systems appear to be more specialized. Especially the
Glossophaginae, a subfamily within the ecologically extremely adaptable New World Leaf-
Nosed bats (Phyllostomidae) evolved into using nectar as their main dietary item. Fruits and
insects form for several species also part of the diet; however, the main morphological and
behavioural adaptations of Glossophagines are only related to nectarivory: An extremely
long tongue and an associated long rostrum allow the access to nectar produced deep within
blossoms; teeth are frequently reduced and flowers are visited in short hovering flights. New
World glossophagine bats are distributed from the Southern United States to Argentina and
live in deserts, rain forests and tropical mountain ranges up to 3000 m. A few species migrate
seasonally in response to the phenology of important food plants, such as Agave spp.
and columnar cactus species. Besides the specialized Glossophagines and the small Antillean
subfamily Phyllonycterinae, there are also a number of opportunistic phyllostomid flower
visitors such as Phyllostomus discolor (Phyllostomidae: Phyllostominae) or Artibeus jamaicensis
(Phyllostomidae: Stenoderminae) that feed mainly on other resources, such as
insects or fruit but may include also nectar from large flowers into their diet.
Main flower preferences
The main motivation for flower-visitation by bats is nectar; only in a few plant species serve
fleshy floral parts as a reward for the visitors (Lord 1991, Tschapka 2003). Pollen is for specialized
nectar-feeding bats an important source of protein that is ingested both directly from
the flower and also indirectly while grooming the fur during nocturnal resting periods. Nightblooming
flowers pollinated by bats both in the New and the Old World are characterized by
– to humans – not very pleasant odours, that have been compared to e.g., the smell of garlic,
mouse urine or human excrements (Dobat & Peikert-Holle 1985). To facilitate the flower
access for the relatively large bats, inflorescences are often raised well above the leaves or
hang on long stalks into the open air space below branches (flagelliflory). At some trees
flowers emerge also directly from the trunk or from larger branches (cauliflory). During the
night bright colours are of less importance for finding flowers, and consequently many batpollinated
flowers are dull brown, green, or purple. Nevertheless, white flowers, such as
those of some columnar cacti in the Mexican deserts (e.g. Stenocereus spp., Pachycereus
spp.), may also provide optical guidance for the bats in these more open habitats. Some
flowers in the Neotropics may even address the bats´ echolocation system by providing particularly
good sound reflecting properties, such as the vine Mucuna holtonii (Fabaceae)
(Helversen & Helversen 1999). Flower visitation by pteropodid bats in the Old World occurs
mainly by landing on the flowers, and the specifically adapted flowers, such as Musa
(Musaceae) or Kigelia (Bignoniaceae) have to be robust enough to support the weight of
their large visitors. The hovering capabilities of the New World Glossophagines, however,
allowed also some of the more fragile plant families to develop mutualisms with pollinating
bats. Consequently Neotropical bats visit robust flowers, such as Agave spp. and Ochroma
pyramidale, but also smaller and more delicate flowers, even from herbs, such as Irlbachia
alata (Gentianaceae), Capanea grandiflora (Gesneriaceae) or Burmeistera spp. (Lobeliaceae).
The latter are exclusively used by the hovering glossophagines, while opportunistic
nectar-feeding phyllostomid bats generally perch on some of the more robust flowers.
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