NECTAR CONSUMERS - Nectaries and Nectar - page 321

Bats are highly mobile pollinators and include migratory species that track
nectar resources. Best known for this is the Mexican bat Leptonycteris cura-
soae , which migrates north, feeding on the nectar of columnar cacti, then
returns south feeding on nectar of Agave species. Its seasonal movement
along a nectar corridor of successively flowering plants in the families Cac-
taceae and Agavaceae was demonstrated by Fleming et al. (1993) using stable
isotope analysis. During peak blooming, the nectar supplied by columnar
cacti in the Sonoran Desert is 3-4 times greater than the energy required by
nectar-feeding bats and birds, which led Fleming et al. (2001) to suggest that
pollinators are limited, a situation which will favour pollinator generaliza-
tion.

The Queensland blossom bat Syconycteris australis is a small megachi-
ropteran (18 g) that is able to meet its energy and nitrogen requirements on a
diet of nectar and pollen only (Law, 1992). Blossom bats and honeyeaters
both drink the remarkably dilute (3-10%) nectar in the brush flowers of the
rainforest tree Syzygium cormiflorum (Myrtaceae). Although they make fewer
and briefer visits to these flowers, the bats are more mobile, carry more pol-
len, and appear to be more effective pollinators (Crome & Irvine, 1986; Law
& Lean, 1999). The importance of energy (rather than nitrogen) as a limiting
resource for Syconycteris australis was confirmed with an energy supple-
mentation experiment that led to an increase in population size (Law, 1995).
It seems more common that nitrogen is a limiting resource for nectar- or
fruit-feeding vertebrates, and Thomas (1984) suggested that two frugivorous
megachiropteran bats might metabolize excess carbon in their diet by increas-
ing their flight activity.

4.4 Other mammals

Opportunistic and sometimes destructive feeding on nectar or entire flowers
has been observed in many non-flying mammals with diverse diets, includ-
ing rodents, marsupials, and primates (Janson et al., 1981), and even giraffes
(Fleming et al., 2006). The ingestion of nectar may be incidental or deliber-
ate. Two Eulemur species studied by Overdorff (1992) in Madagascar treat
the same flowers differently, rufous lemurs consuming entire flowers and
red-bellied lemurs licking the nectar without damaging the flowers; only the
latter were considered to be potential pollinators. Nectar may sustain frugi-
vorous primates during times of food scarcity (e.g., Gautier-Hion & Maisels,
1994) and may also be a water resource. The very dilute nectar (~10%)
of Aloe marlothii (Asphodelaceae) can be highly desirable to baboons,
Papio hamadryas, because it flowers during dry winters in South Africa
(C.T. Symes and S.W. Nicolson, unpublished). Other plant exudates are less