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Patterns of plant visitation by nectar-feeding lizards

  • Erell Institute

Abstract and Figures

Geckos in the genus Hoplodactylus visit flowers to feed on nectar. I examined the patterns of flower visitation exhibited by two gecko species (H. maculatus and H. duvauceli) having access to two plant species: pohutukawa (Metrosideros excelsa: Myrtaceae) and flax (Phormium tenax: Agavaceae). Individual geckos were not observed to visit both plant species; individuals visiting flax tended to revisit the same plant. Geckos visiting pohutukawa were larger than those visiting flax and exhibited an early night peak in plant visitation, while lizards on flax displayed a more even pattern of activity throughout the night. On flax, geckos were more likely to be found on plants with a greater number of male flowers. Male flax flowers were of greater diameter than female flowers and produced nectar at higher rates and with greater concentrations of sugars. Experimental manipulation of pohutukawa nectar volumes suggested that the distribution of geckos is influenced by the pattern of nectar availability.
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Oecologia (1995) 101: 228-233
? Springer-Verlag 1995
Douglas A. Eifler
Patterns of plant visitation by nectar-feeding lizards
Received: 15 July 1994 / Accepted: 30 September 1994
Abstract Geckos in the genus Hoplodactylus visit flow-
ers to feed on nectar. I examined the patterns of flower
visitation exhibited by two gecko species (H. maculatus
and H. duvauceli) having access to two plant species:
pohutukawa (Metrosideros excelsa: Myrtaceae) and flax
(Phormium tenax: Agavaceae). Individual geckos were
not observed to visit both plant species; individuals visit-
ing flax tended to revisit the same plant. Geckos visiting
pohutukawa were larger than those visiting flax and ex-
hibited an early night peak in plant visitation, while liz-
ards on flax displayed a more even pattern of activity
throughout the night. On flax, geckos were more likely
to be found on plants with a greater number of male
flowers. Male flax flowers were of greater diameter than
female flowers and produced nectar at higher rates and
with greater concentrations of sugars. Experimental ma-
nipulation of pohutukawa nectar volumes suggested that
the distribution of geckos is influenced by the pattern of
nectar availability.
Key words Foraging ? Lizard ? Nectarivory ? Gecko
The diet and foraging strategies of animals tend to be ef-
ficient, reflecting cost-benefit criteria in such a way that
alternatives are chosen that yield more food per time unit
(Stephens 1990). To forage efficiently, animals need to
adapt their behavior to available food resources, detect-
ing patterns in food dispersion and tracking changes in
resource availability. Response to patterns of food dis-
persion should be evident when dealing with food types
to which an animal is specialized or where a food type
represents an important diet component (Real and Cara-
co 1986).
The ability to assess nectar availability and quality
has been extensively studied for a variety of vertebrates.
Nectarivorous birds can distinguish among nectars dif-
fering in sugar composition or concentration, and among
nectar sources available with differing degrees of vari-
ance (Wunderle and O'Brien 1985; Martinez del Rio
1990). In response to nectar supplementation, humming-
birds alter their activity patterns and focus foraging ef-
fort in areas with abundant nectar (Gass and Sutherland
1985). Members of several families of nectarivorous
birds vary the degree to which they defend territories in
response to manipulation of nectar availability (Gill and
Wolf 1975a; Carpenter and MacMillen 1976; Kodric-
Brown and Brown 1978). Similar behavioral changes oc-
cur among nectarivorous mammals. Some species, such
as the marsupial glider, Petaurus australis, simply
choose to forage at trees with a higher flower abundance
to increase foraging efficiency (Goldingay 1990). Other
species show more complex responses to changes in nec-
tar availability. The long-nosed bat, Glossophaga soric-
ina, switches between territorial defense of nectar sourc-
es and trapline foraging as nectar availability changes
(Lemke 1984). Among tamarin monkeys, the location
and size of territories may be linked to the availability
of seasonally important nectar sources (Terborgh and
Stern 1987).
Most lizard species are exclusively insectivorous or
herbivorous (Greene 1982). Insectivorous and herbivo-
rous lizards may alter their behavior in response to chan-
ges in food availability, modifying home ranges (Simon
1975; Stamps and Tanaka 1981; Guy er 1988), foraging
behavior (Munger 1984), and activity patterns (Wald-
schmidt 1983; Jones et al. 1987) as well as distinguish-
ing among foods of differing quality (Troyer 1984; Ea-
son 1990). Several species of lizard have been recorded
feeding on nectar (Cheke 1984; Whitaker 1987a; Greer
1989). The extent to which nectar is an important food
source for these lizards is unknown. While many animals
specialized for nectar feeding can evaluate and track nee-
D.A. Eitler1
Museum of Comparative Zoology, Harvard University,
Cambridge, MA 02138, USA
1 Present address:
Museum of Natural History, University of Kansas, Lawrence,
KS 66045, USA
tar quality and quantity (Kearns and Inouye 1993), the
role of nectar in lizard energetics and the extent to which
nectar availability is a resource that lizards evaluate and
track is unclear (Greer 1989).
In New Zealand, nocturnal Hoplodactylus geckos take
nectar from a variety of plants (Whitaker 1987a). The
purpose of this study was to determine the extent to
which patterns of flower visitation by Hoplodactylus
geckos reflect patterns of nectar availability. I focused on
geckos visiting two flowering plant species: flax (Phor-
mium tenax: Agavaceae) and pohutukawa (Metrosideros
excelsa: Myrtaceae), identifying the patterns of activity
displayed by geckos visiting flowers, the distribution of
geckos within and between plant species, and the rela-
tionship of nectar availability and plant characteristics to
gecko distributions.
Materials and Methods
Study site and study organisms
The study was conducted on Korapuki Island, an 18 ha island ap-
proximately 10 km east of the Coromandel Peninsula, North Is-
land, New Zealand. Pohutukawa is the dominant canopy plant,
while flax is the dominant plant bordering beaches. Pohutukawa is
a large tree (up to 20 m) found mainly along sea coasts and lake
shores (Laing and Blackwell 1950). The shallow cup-like flowers
remain open for 6-8 days and are arranged in cymes; flowers
within the cyme open sequentially so that a single inflorescence
blooms for up to 12 days (Whitaker 1987a). Individual trees may
be in flower up to 6 weeks, and within a population the flowering
season may last 6-10 weeks (Whitaker 1987a). Pohutukawa trees
produce large amounts of nectar and are visited by birds and bees
(Moore and Irwin 1978). Geckos are known to accumulate at
flowering pohutukawa trees in large numbers, with as many as 5-8
geckos/m2 of canopy (Whitaker 1968, 1987a,b).
Flax is a large monocot endemic to New Zealand. The tubular
flowers are arranged in raceme-like stalks averaging approximate-
ly 3 m in height; flowers are protandrous hermaphrodites produc-
ing large quantities of relatively dilute nectar (Craig and Stewart
1988). Male and female flowers may be present on the same inflo-
rescence (Craig and Stewart 1988). Nectar feeding birds common-
ly visit flowers, preferring to visit male flowers (Craig 1989).
Male flowers in populations of flax near Auckland contain higher
volumes of nectar of higher sugar concentration than female flow-
ers (Craig and Stewart 1988). Geckos have been observed to feed
on flax nectar. At some sites every flower stalk may have geckos,
with densities as high as 4-6/stalk (Whitaker 1987a,b).
Hoplodactylus geckos are nocturnal lizards using terrestrial and
arboreal habitats and are considered to be primarily insectivorous
(Bull and Whitaker 1975). Two species, H. duvauceli and H. macu-
latus, occur on Korapuki Island (Towns 1991). H. duvauceli is the
larger of the two study species, with adult snout-vent lengths
(SVL) ranging from 100 to 160 mm and weights ranging from 40
to 118 g (Whitaker 1968; Barwick 1982). Previous reports of adult
H. maculatus SVL range from 45 to 71 mm and weights range
from 4 to 14 g (Whitaker 1982a; Gill 1986; Towns 1991). A tran-
sect running approximately 200x5 m along the beach and shoreline
comprised the study area. Observations focused on geckos visiting
flax that lined the transect and on the lower 2 m of a single poh-
utukawa tree on the transect that was in flower during the study.
Nectar and floral characteristics
Standing nectar crop was measured with 100 ?? pipettes, and sugar
concentrations were measured with a Reichert 10430 temperature
compensated refractometer (Leica, Buffalo, NY). Measurements
on standing nectar crop and nectar concentration were made from
2100 to 2400 hours. Rates of nectar production and sugar concen-
tration of new nectar for male and female flax flowers were com-
pared by first draining the nectar from pairs of male and female
flowers on the same stalk, enclosing the flowers in white mesh
bags, and measuring nectar volume and concentration after 24 h.
The size of male and female flax flowers was compared using the
maximum flower diameter below the point where the sepals
formed a continuous tube.
Gecko activity and distribution patterns
I determined activity periods for geckos by walking a predeter-
mined census route every hour from 1 h before dark until sunrise
and recording the number of lizards present on flax and poh-
utukawa. The size distribution of lizards on the two plant species
was assessed by collecting geckos from plants and weighing them.
I individually marked lizards with a paint pen, then recorded the
individual plants on which they were resighted to determine indi-
vidual patterns of plant use. When observing lizards on flax
plants, I recorded the sex of flowers visited and whether the liz-
ards fed at the base of flowers or in the corolla. Observations were
made using red filtered light.
The relationship of nectar availability and plant characteristics
to gecko distributions
To identify characteristics of flax plants visited by geckos, I mea-
sured variables from 50 flax stalks on the transect; on the evening
following these measurements I censused the plants to see which
were visited by geckos. During the evening of censusing, I also
observed geckos on nine unmeasured stalks. These stalks were
measured the next morning. The following characteristics were
identified for the 59 flax stalks: stalk height (m), number of flow-
ers of each sex present, nearest stalk (m; at 1.5 m height), nearest
stalk from another flax plant (m; at 1.5 m height), and number of
stalks belonging to the plant. Sometimes the nearest stalk was also
the nearest stalk from another plant.
I evaluated the effect of flower distribution on the distribution
of geckos visiting pohutukawa by comparing gecko sightings at
six discrete patches of inflorescences, varying in inflorescence
number from 8 to 63, for 3 nights of censusing. As patches varied
noticeably in canopy surface area, I tied away nearby branches so
that the patches were not contiguous with the canopy surface to
avoid simply documenting an area effect. Lizards had to enter
each inflorescence patch from the interior of the tree along main
branches (similar to an animal choosing among the arms of a radi-
al maze).
I experimentally manipulated pohutukawa nectar availability to
examine its effect on lizard distribution. From the above six inflo-
rescence patches, the three with the most inflorescences were each
partitioned into a manipulated and unmanipulated half. Prior to
manipulation, the three patches were censused for 2 nights and the
number of lizards visiting each patch half was determined. Next,
artificial nectar (56.5% sucrose solution; approximately the aver-
age pohutukawa nectar concentration observed during this study)
was used to supplement the nectar available in the flowers of the
manipulated half of each patch. Sucrose solution was added to
15% of the flowers and was added until the flower was full of liq-
uid (an addition averaging approximately 25 ?? sucrose solu-
tion/flower). Sucrose solution was added to flowers just before
sunset for 3 days. During the night following the last 2 days, I
censused patches to determine the number of lizards visiting ma-
nipulated and unmanipulated patch halves.
Results are presented as means ?SE. Statistical tests used are
identified in the text and were performed using Minitab (State
College, Pa.).
Nectar and floral characteristics
The concentration and volume of standing flax nectar
were determined for male and female flowers at the be-
ginning of the night. There was no significant difference
in nectar sugar concentration between male flowers
(21.6 ? 0.34% sugar) and female flowers (20.3 ? 0.88%
sugar; Mann-Whitney test: U = 164, ? = 9 and 13, re-
spectively, ? = 0.34). Nor was there a significant differ-
ence in the standing nectar volume of male versus female
flowers (Mann-Whitney test: U = 72, ? = 6 and 9, respec-
tively, ? = 1.0). Male flowers contained 95.3 ? 31.8 ?? of
nectar whereas females contained 83.1 ? 30.3 ??. Male
flax flowers had a greater maximum diameter than fe-
male flowers (11.8 ? 0.2 mm versus 10.0 ? 0.2 mm;
Mann-Whitney test: U = 215, ? = 8 and 14, respectively,
? = 0.0003).
Male flax flowers exhibited a significantly greater
rate of nectar accumulation than female flowers of the
same plant (Wilcoxon's signed rank: ? = 55, ? = 0.006);
the 24-h nectar production of males averaged almost 3
times that of females (males flowers 264.3 ? 35.6 ?? ver-
sus females 98.5 ? 35.5 ??). Although sugar concentra-
tion in standing nectar crop does not vary among male
and female flax flowers, sugar concentration in new nec-
tar produced by male flax flowers was significantly high-
er (19.62 ? 1.07% sugar) than that produced by female
flowers (15.36 ? 1.48% sugar; Wilcoxon's signed rank:
T= 27, ? = 0.035).
Nectar from pohutukawa was more viscous and diffi-
cult to remove from flowers than flax nectar. To sample
flowers more easily, nectar sampling was biased towards
flowers with the most abundant supplies. For the 75
flowers sampled, nectar volume ranged from 25.8 to
61.53 ??. Average sugar concentration for pohutukawa
nectar was 53.22 ? 1.5%. Pohutukawa nectar contained a
higher sugar concentration than flax nectar (flax
21.09 ? 0.42%; Mann-Whitney test: U = 253, ? = 22 and
72, respectively, ? = 0.0001). Inflorescences contained
32.48 ?2.13 flowers.
Gecko activity and distribution patterns
During 3 nights of all-night censusing, 106 sightings of
H. maculatus were made on flax and 131 on the poh-
utukawa. Hourly censuses were conducted from 2000
to 0500 hours; lizards were found during the
2100-0400 hour sampling periods. The distribution of
sightings on flax versus pohutukawa was significantly
different (?2 = 30.45, =1,P< 0.001; Fig. 1). Lizard
activity on flax did not differ from an even distribution
throughout the night (?2 = 7.66, =7, ? = 0.36). Ac-
tivity on the pohutukawa was not evenly distributed
(?2 = 54.09, = 7, ? < 0.001), exhibiting a pro-
nounced peak at 2200 hours followed by a steady de-
cline in activity (Fig. 1). A marked difference in the
Time of
day (h)
Time of
day (h)
Fig. 1 Distribution of Hoplodactylus maculatus sightings on flax
and pohutukawa plants at different times of day
0-2 4-6 8-10 12-14 16-18
2-4 6-8 10-12 14-16
Body Mass (g)
Fig. 2 Frequency distribution of body mass of Hoplodactylus mac-
ulatus found visiting flax or pohutukawa plants
size of H. maculatus captured on flax versus poh-
utukawa was observed (Fig. 2); lizards foraging on flax
were smaller (5.0 ? 0.7 g) than those found on poh-
utukawa (12.2 ? 2.1 g; population range 1.4-17.9 g;
Mann-Whitney test: U = 996, ? = 37 and 58, respective-
ly, ? < 0.0001). No H. duvauceli were found foraging
on flax; those found on pohutukawa averaged
65.6 ? 4.4 g (range: 57-72 g). Two or three geckos
were often observed on the same flax stalk or poh-
utukawa inflorescence. In these instances, I did not ob-
serve any obvious aggression, avoidance, or other
forms of interaction.
Nineteen H. maculatus were resighted on different
days for a total of 64 observations. No individual lizard
was ever recorded from both flax and pohutukawa. Of
the nine geckos resighted on flax 34 times, five were al-
ways resighted on the stalk from which they were origi-
nally captured and the other four were recorded from
two stalks belonging to the same plant. The process of
capturing and marking appeared to disturb the geckos.
Table 1 Characteristics of flax plants at which geckos were and
were not observed. Measurements are presented as mean ? SE;
? = 42 with geckos absent, 17 with geckos present. Statistical
comparisons were made using the Mann-Whitney test
Variable Absent Present U
2.04 ?0.05 1.93 ?0.11 469 0.490
2.36 ?0.37 7.18 ?1.70 684 0.004
18.40 ?1.90 19.60 ?4.10 505 0.940
0.60 ?0.05 0.67 ?0.16 488 0.710
2.62 ?0.48 1.97 ?0.30 527 0.780
Number of plant stalks 2.45 ? 0.19 3.18 ? 0.47 587 0.190
Stalk height (m)
of male flowers
of female flowers
Nearest stalk (m)
Nearest plant (m)
10 20 30 40 50
Inflorescence number 60 70
? (Exponential Fit)
Fig. 3 Relationship between the number of inflorescences in a
pohutukawa patch and the log number of geckos observed within
the patch. Regression equation: y = 0.205* + 0.554, r2 = 0.909,
? = 0.003
As a result I stopped the process after 2 nights, only
marking a portion of the population sighted.
At the end of the study period, I recorded details con-
cerning the behavior of foraging lizards. Prolonged ob-
servations were not feasible; although working with a
red light seemed to reduce disruption of gecko behavior
many animals still sought refuge after only several sec-
onds of observation. Geckos were never observed eating
anything other than nectar during this study. The sex of
flax flowers being visited as well as the method of nectar
extraction was recorded for 15 geckos. Foraging lizards
used different methods while attempting to remove nec-
tar from male versus female flowers. Four lizards were
observed while feeding on male flowers; they all fed by
pressing their head into the corolla. Eleven lizards were
observed while feeding on female flowers; they all fed
by licking the outer base of the corolla. The small ex-
pected values generated by this distribution precludes
statistical analysis of these observations.
Of the 15 geckos for which the sex of visited flower
was determined, 4 were feeding on stalks where flowers
of both sexes were present. All 4 were feeding at male
flowers. There were a total of 6 male and 26 female
flowers on these four stalks. If flower choice were ran-
dom with regard to flower sex, the probability that all 4
lizards would have been found at male flowers is
? = 0.0125 (binomial distribution), indicating that geck-
os were preferentially feeding at male flowers.
The relationship of nectar availability
and plant characteristics to gecko distributions
Six measurements of flax stalks were compared for
plants where lizards were found foraging and those
where lizards were not observed (Table 1). The only
characteristic that differed significantly was the number
of male flowers; the stalks with lizards had significantly
more male flowers than stalks not visited by lizards.
A linear regression of the logarithm of gecko number
against the number of pohutukawa inflorescences in a
patch was calculated using 4 nights of censusing (Fig. 3).
Variation in the number of geckos present in a region of
the pohutukawa tree was sensitive to the number of in-
florescences present (r2 = 0.909, ? = 0.003).
Before nectar manipulation, geckos were evenly dis-
tributed between control and experimental pohutukawa
patches (31 versus 30 geckos per patch). During the ex-
perimental nectar addition, a marginally higher propor-
tion of geckos was found in areas where nectar had been
added (23 in control versus 43 in supplemented;
?2 = 330, = 1, ? = 0.069).
Gecko distributions within plant species
Gecko visits to flowers appear to be based on an evalua-
tion of nectar availability. For flax plants, male flowers
secrete nectar at higher rates and in higher concentra-
tions than female flowers. Geckos tend to return to the
same flax stalks and were observed to feed preferentially
on male flax flowers. By choosing stalks with large num-
bers of male flowers, geckos can take advantage of great-
er rates of nectar replenishment to obtain nectar at high
rates with minimal travel. In some instances, male flower
standing nectar volume and sugar concentration are
greater than female flowers (Craig and Stewart 1988)
and would offer an even greater advantage to the male
flower preference detected in this study. Male flower
preference is displayed by other vertebrates; nectar feed-
ing birds also prefer male flax flowers (Craig 1988).
The distribution of lizards at inflorescence patches
within a single pohutukawa tree also reflects nectar
availability. As inflorescence numbers per patch increas-
es, gecko numbers increase exponentially, indicating an
attraction to greater numbers of flowers. The observed
trend for geckos to switch their attention to areas of nec-
tar-supplemented flowers offers additional support that
geckos monitor and respond to changes in nectar avail-
The distribution of geckos between plant species
Pohutukawa trees appear to offer greater opportunities
for nectar feeding than flax, offering nectar with higher
sugar concentrations and in greater abundance than indi-
vidual flax plants. Several factors need to be considered
concerning the observed distribution of small lizards pre-
dominately on flax and larger individuals on pohutukawa
(Fig. 2). First, the observed distributions could reflect
size-related differences in mobility; perhaps larger geck-
os may be more able or inclined to travel to the poh-
utukawa trees than smaller individuals. Since there was
only one pohutukawa tree flowering in the study area,
most geckos on the study site would have to travel in or-
der to feed on pohutukawa nectar. While the distance
needed to travel may have acted as a hinderance, it is not
likely to be the only factor involved. Small geckos were
found foraging on flax adjacent to the pohutukawa tree.
Hoplodactylus geckos may travel long distances from
pohutukawa trees, sometimes travelling over 50 m (Whi-
taker 1987a). Also, small H. maculatus appear more
likely to move longer distances than larger individuals
(Whitaker 1982a).
Second, the size of foraging geckos may influence
their ability to extract nectar from the two plant species.
The costs of using different flower types varies with
body size in nectarivorous sunbirds (Gill and Wolf
1975b). Pohutukawa nectar can be easily removed from
its shallow open-faced flowers, but the long tubular flax
flowers may represent a challenge to foraging geckos.
Whitaker (1987a) reports on adult H. duvauceli feeding
on flax and suggested that flax flowers are so robust that
only large geckos could force their petals apart to feed
on their nectar. However, in this study only the smaller
individuals of the smaller species, H. maculatus, were
observed on flax. If larger geckos are able to feed on
flax, then their absence from flax flowers appears to be
from choosing pohutukawa over flax. Because poh-
utukawa trees seem to offer more accessible nectar than
flax, smaller geckos could obtain nectar more efficiently
from pohutukawa. Thus, ability to extract nectar from
flowers does not account for the presence of small geck-
os on flax and larger ones on pohutukawa.
Finally, pohutukawa may be the nectar source best
suited to all size classes but smaller individuals may be
avoiding large H. maculatus and H. duvauceli. The pres-
ence of large gecko species can result in a habitat shift
among smaller species (Petren et al. 1993) and may lead
to pr?dation on smaller geckos (Bauer and DeVaney
1987; Bolger and Case 1992). Competitive displacement
has been suggested for other nectar feeding lizards.
While feeding on flower nectar, large Phelsuma sund-
berg geckos will displace smaller individuals (in Cheke
1984) and interspecific encounters among Phelsuma
geckos may result in the exclusion of smaller species
from access to nectar (in Cheke 1984). In at least one in-
stance, H. maculatus has been found in the stomach con-
tents of H. duvauceli (Barwick 1982) and H. maculatus
(Whitaker 1982b).
Of the three factors discussed above, size-related dif-
ferences in mobility and nectar extraction ability do not
account for the pattern of lizards distributions on the two
plant species. The only explanation consistent with my
results is that larger geckos use the more valuable nectar
source (pohutukawa), while smaller individuals avoid
larger geckos and settle for feeding on flax.
Gecko activity patterns
Differences in the activity patterns of flax- and poh-
utukawa-feeding geckos may reflect differences in quali-
ty of the two plant species as nectar sources. Because of
the larger number of flowers and the more concentrated
nectar, geckos on pohutukawa may be able to obtain sati-
ating levels of nectar quickly, resulting in a more peaked
activity pattern (Fig. 1
). The more dilute flax nectar, rel-
atively fewer number of flowers, and less accessible
nectar may make satiation at flax plants a more time
consuming process resulting in the more protracted, even
activity pattern. Most pohutukawa flowers still contain
nectar at the end of the night, so geckos probably do not
show a shorter span of activity on the pohutukawa be-
cause they have exhausted the available nectar. In nectar-
ivorous bird communities, larger species that control ac-
cess to the most rewarding nectar sources spend less time
foraging (Collins et al. 1990).
The results of my study indicate that geckos tend to
use the most profitable nectar sources and that nectar
sources are subject to intra- and interspecific partition-
ing. While nectar seems to be an important resource for
geckos, further studies are required before this is sub-
stantiated and the nature of the interaction between the
geckos and plants is fully understood. More complete
compositional analysis of the types of nectars taken by
geckos will reveal the extent to which their nutritional
needs are met by consuming nectar. Such studies need
to be coupled with those on the energetics of geckos
and their foraging activities away from nectar sources
to delineate the role of nectar in the life history of these
geckos. Finally, the potential impact of the geckos on
the life history of flax and pohutukawa needs to be ad-
dressed. Pollen collects on geckos visiting these plants
(Whitaker 1987a), suggesting that Hoplodactylus may
play a role in pollination. Furthermore, nectar depletion
resulting from large numbers of geckos visiting flowers
may affect the energetics of these plants or limit
their ability to attract pollinators. The extent of the
interaction between these organisms remains to be in-
Acknowledgements I thank Phil and Sue Thomson for assistance
on Korapuki. The New Zealand Department of Conservation pro-
vided logistical support and granted permission to work on Ko-
rapuki. Tony Whitaker provided advice that made this study possi-
ble. Maria Eifler and two anonymous reviewers provided helpful
discussion and comments on the manuscript. This work was sup-
ported by a Putnam Expedition Grant from the Museum of Com-
parative Zoology, Harvard University.
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... For example, several species of Lygodactylus that are endemic to Madagascar and north-eastern Brazil are known to consistently ingest plant exudates such as resin, sap, and gum (Folling et al. 2001;Teixeira et al. 2013). Similarly, geckos from New Zealand and New Caledonia frequently consume sugary exudates and are attracted to plants with nectar-producing inflorescences (Eifler 1995;Evans et al. 2015). ...
... A growing body of literature shows not only that geckos are attracted to nectar-producing inflorescence but also that geckos can play a significant role in pollination and seed dispersal within ecosystems (Bauer and Sadlier 1994;Hansen et al. 2007;Hopkins et al. 2015;Tanalgo and Hughes 2017). Despite the opportunistic nature of many lizard-plant interactions, such indirect mutualisms can provide significant benefits to the host plant (Eifler 1995;Hopkins et al. 2015;Tanalgo and Hughes 2017). For example, when geckos attend flowers, direct contact with stigmas results in pollen adhering to gecko snouts/throats and enables cross-pollination when multiple flowers are visited (Evans et al. 2015;Hansen et al. 2007;Hopkins et al. 2015). ...
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The diets of many animals are influenced by resource availability, competition, and evolutionary selected traits enabling the utilization of palatable foods. Omnivores are species that maintain their macronutrient balance by supplementing highly abundant but poor nutritional quality food items, with sporadically available but high nutritional quality food items. Although there are anecdotal observations of Australian geckos (Lacertilia: Gekkonidae) consuming plant exudates, the consumption of plant material has long been considered to be anomalous behavior among Australian geckos. Here, we test the idea that sap feeding may not be anomalous behavior but instead a dietary niche of geckos that has gone unappreciated due to constraints on the methods used to quantify geckos’ diets. We tested this idea by investigating the consumption of Acacia victoriae gum by the gecko Gehyra versicolor using timed searches and time-lapse photography. We found that geckos frequently consumed gum, and G. versicolor numbers were five times greater on A. victoriae trees that exhibited significant gum bleeds compared to gecko numbers on non-bleeding trees. Taken together, our observations that G. versicolor spp. frequently feed on gum along with anecdotal reports of geckos consuming gum provide compelling evidence that gum/sap feeding is not anomalous behavior and suggest that many Australian gecko species are omnivores whose diets include plant exudates and animal prey.
... Male and female G. wislizenii differed in both their movements and habitat use. The standard measures of lizard movement (MPM and PTM) and 1-min displacement distances did not vary by sex, but MPM and PTM have increasingly been found to be inadequate for describing the range and adaptive characteristics of movement patterns (Eifler andEifler, 1999a, 1999b;Butler, 2005;McElroy et al., 2011). Using different metrics, we found a significant difference between the sexes in displacement sequences and in the distribution of movement durations. ...
... Intraspecific variation in habitat use has been observed repeatedly in lizards, both between sexes (Hebrard and Madsen, 1984;Eifler et al., 2007) and among size or age classes (Stamps, 1983;Wikelski and Trillmich, 1994;Eifler, 1995). Variation in habitat use can be associated with social activities, foraging, predation risk, and physiological considerations (Stamps, 1983), potential interconnections that are not necessarily mutually exclusive (Andrews, 1971;Scott et al., 1976;Stamps, 1977). ...
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We studied the long-nosed leopard lizard, Gambelia wislizenii, in the Great Basin Desert of southeastern Oregon to identify intraspecific patterns of behavioral variation. Sex and body size played an important role in determining intraspecific behavioral differences. Males and females showed different habitat preferences, with males spending more time on hardpan and in the center of shrubs. Males made more long moves and clustered their long moves more frequently than females. Smaller lizards displayed more head turns, tongue flicks, and use of elevated perches. Smaller individuals also spent a higher proportion of time moving.
... Pollination by lizards are reported in harsher climate, Elvers (1977) worked on lizard's role in pollination, and is the first to establish the fact on the basis of field observation that lizards were visiting flowers of Musschia aurea (Campanulaceae) in order to feed on nectar and thereby pollinating them as a side function in the Portuguese island of Madeira. Ever since that, the role of lizards as pollinator and seed disperser is being emphasised upon by many groups of researchers (Eifler 1995;Nyhagen et al. 2001;Olsson et al. 2000;Traveset 1995;Traveset & Sa´ez 1997;Valido & Nogales 1994;Whitaker 1987). Celedün- Neghme et al. (2016) worked on pollinators of Mediterranean species Ephedra fragilis and found a native lizard Podarcis lilfordi (Lacertidae) contributed to enhancement of this plant's reproductive success. ...
... Pollination by lizards are reported in harsher climate, Elvers (1977) worked on lizard's role in pollination, and is the first to establish the fact on the basis of field observation that lizards were visiting flowers of Musschia aurea (Campanulaceae) in order to feed on nectar and thereby pollinating them as a side function in the Portuguese island of Madeira. Ever since that, the role of lizards as pollinator and seed disperser is being emphasised upon by many groups of researchers (Eifler 1995;Nyhagen et al. 2001;Olsson et al. 2000;Traveset 1995;Traveset & Sa´ez 1997;Valido & Nogales 1994;Whitaker 1987). Celedün- Neghme et al. (2016) worked on pollinators of Mediterranean species Ephedra fragilis and found a native lizard Podarcis lilfordi (Lacertidae) contributed to enhancement of this plant's reproductive success. ...
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Ethnoecological surveys and field studies are important for systematic documentation. The present study is based on the findings of ethnoecological surveys conducted in the two districts of the UT of Ladakh in Indian Western Himalaya to highlight the traditional uses of the genus Ephedra L. (Ephedraceae) by the native people. Results revealed that the local communities of both Leh and Kargil districts have a great respect for and faith in Amchi system of medicine practiced in the entire region. Our study revealed some new or lesser known medicinal, cultural, ecological uses of Ephedra as well as faunal interactions with Ephedra that are new addition to the knowledge from the Western Himalaya.
... Moreover, lizards preferred hermaphrodite over male flowers, possibly attracted by their higher nectar production (although the patterns of nectar secretion should be assessed more precisely in further studies), whereas insects visited higher proportions of male flowers. A previous study in New Zealand (Eifer 1995), specifically with the perennial herb Phormium tenax, already reported flower selection by geckos as a function of nectar production. A higher visitation of hermaphrodite flowers might in turn increase plant fruit crop, as these flowers are those developing into fruits. ...
... Both Raukawa and Duvaucel's geckos have been observed feeding on Metrosideros nectar at peak flowering (Eifler, 1995;Evans et al., 2015). There is, however, strong evidence of resource partitioning between species, with Evans et al. (2015) suggesting that, overall, flax nectar may be a more significant nectar source for Raukawa gecko, and honeydew more important for Duvaucel's gecko. ...
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Myrtle rust (Austropuccinia psidii (G. Winter) Beenken) was detected on the New Zealand mainland in May 2017. Myrtle rust was first described in Brazil in 1998, and since then has spread throughout the Americas, to Asia, Africa, the Pacific islands, and most recently to Australia, causing a global pandemic. A. psidii is a pathogen of the Myrtaceae family, and attacks young leaves, shoots, stems and flowers. Given overseas experience with the pathogen, a wide range of host species in New Zealand are expected to have the potential to be infected. In New Zealand, the optimal conditions for myrtle rust are predicted to be confined to mainly coastal and the northern areas of the North Island. In these areas, Myrtaceae species, principally pōhutukawa Metrosideros excelsa, kānuka Kunzea robusta and mānuka Leptospermum scoparium are common, and may dominate plant communities. The aim of this review is to consider the potential longer-term impact of myrtle rust, with a focus on the flow-on effect to indigenous New Zealand fauna, particularly the nectarivorous species that use myrtaceous flowers as a food source. This potential is explored through a case study of Tiritiri Matangi Island, an ecological restoration project in the Hauraki Gulf, northern New Zealand. Although any degradation or loss of the Myrtaceae will have long-term and potentially devastating impacts on the myrtaceous habitats and allied fauna, we suggest that niche flexibility associated with much of the New Zealand fauna bodes well for such future environmental challenges. Fauna with an obligate relationship with Myrtaceae, however, may be at greatest risk from the pathogen’s establishment. Management options are suggested to mitigate the impact of myrtle rust on nectarivorous fauna.
... A elevada competição intraespecífica, que resulta das grandes densidades que estas espécies podem atingir em ilhas sem predadores (Markwell e Daugherty, 2002), é também um fator que pode levar à diversificação da dieta. Muitos destes répteis assumem o papel de polinizadores (Whitaker, 1987;Eifler, 1995;Traveset e Sáez, 1997, Nyhagen et al., 2001 e dispersores de sementes (Valido e Nogales, 1994;Traveset, 1995;Whiting e Greff, 1997;Lord e Marshall, 2001;Godínez-Álvarez, 2004), sendo indispensáveis para a sobrevivência de muitas espécies endémicas das ilhas (Valido e Olesen, 2010). As osgas diurnas do género Phelsuma, por exemplo, são as principais responsáveis pela polinização de muitas plantas endémicas em Madagáscar (Minnaar et al., 2013;Gardner e Jasper, 2015). ...
The majority of seabird species nests in oceanic islands, having an important role in the dynamics of these insular ecosystems due to marine nutrient inputs. On these islands, the existence of terrestrial reptiles is very common, and these may reach high densities due to the absence of predators. Therefore, increased intraspecific competition leads to diet diversification, leading to more frequent herbivory among insular reptiles. The Madeira wall lizard, Teira dugesii selvagensis, is a partially herbivorous species that also predates Cory shearwater chicks, having an impact of 5% on the reproductive success of this seabird at the island of Selvagem Grande. This study aims to characterize and compare the population structure of Madeira wall lizards, as well as its role in the trophic web of various areas of Selvagem Grande. These areas were designated according to the type of relief, size of seabird colonies and vegetation cover, in two different Cory shearwater nesting seasons (egg incubation and offspring feeding period). The abundance of lizards in different areas and in both seasons was estimated using capture-mark-recapture. Lizard droppings were also collected, to identify contents. Samples of species belonging to the Selvagem Grande trophic chain were collected for isotopic analysis. Isotopic results were analyzed using SIAR and SIBER packages. Both the highest abundance of lizards and the highest vegetation cover were found in areas with small seabirds colonies. In spite of that, the proportion of lizard immatures was higher on the South/Southwest facing cliffs, where the largest seabird colonies are located. Herbivory increases with lizard size, and there was a high percentage of vegetable contents (about 65%) in the droppings. The isotopic basis of the trophic chain varied significantly among areas and is probably influenced by island topography and seabird inputs. Comparing signatures between geckos and lizards of the island, allowed the characterization of niches occupied by each species, being the differences justified by their diets. In areas with larger seabird colonies, seabirds or nutrient inputs brought by them were extremely important for the diet of T.d. selvagensis. The lizards with smaller differences in their isotopic niche between seasons were found in the areas with most seabirds, while the highest isotopic niche differences occured where resources were fewer. Isotopic results validate the dropping analysis, indicating consumption of seabirds during the bird offspring feeding period. Results obtained in this study suggest that the pressure of lizards on seabirds colonies is variable along the island. In contrast to what was expected, in areas with more vegetation there was a reduced impact on seabirds, despite higher abundances of lizards. Lizard monitorization should be continued to assess population trends as vegetation recovers after the eradication of rabbit and domestic mouse.
... Intraspecific variation in habitat use has been observed repeatedly in lizards, both between the sexes (Capel-Williams & Pratten 1978; Hebrard & Madsen 1984) and among size or age classes (Stamps 1983a;Wikelski & Trillmich 1994;Eifler 1995;Wymann & Whiting 2002). Variation in perch height typically involves males using higher perches than females (Schoener 1968;Perry 1996;Anibaldi et al. 1998) and adults using higher perches than juveniles (Andrews 1971;Perry 1996;Keren-Rotem et al. 2006), which is consistent with our findings. ...
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We characterized the habitat use and movement patterns of adult male, adult female and juvenile Pseudocordylus capensis, a diurnal, rock-dwelling, insectivorous lizard. Rock use was vertically stratified: males spent most of their time at local high points, females at mid-level on the rocks, and juveniles were typically in the lower regions. Movement patterns varied with demographic class as well: juveniles moved more frequently and spent a greater proportion of their time in motion than did adults, and the number of moves of different durations varied among the classes. Finally, juveniles scanned their surroundings and appeared to feed more frequently than adults.
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Nectar‐feeding birds provide an excellent system in which to examine form‐function relationships over evolutionary time. There are many independent origins of nectarivory in birds, and nectar feeding is a lifestyle with many inherent biophysical constraints. We review the morphology and function of the feeding apparatus, the locomotor apparatus, and the digestive and renal systems across avian nectarivores with the goals of synthesizing available information and identifying the extent to which different aspects of anatomy have morphologically and functionally converged. In doing so, we have systematically tabulated the occurrence of putative adaptations to nectarivory across birds and created what is, to our knowledge, the first comprehensive summary of adaptations to nectarivory across body systems and taxa. We also provide the first phylogenetically informed estimate of the number of times nectarivory has evolved within Aves. Based on this synthesis of existing knowledge, we identify current knowledge gaps and provide suggestions for future research questions and methods of data collection that will increase our understanding of the distribution of adaptations across bodily systems and taxa, and the relationship between those adaptations and ecological and evolutionary factors. We hope that this synthesis will serve as a landmark for the current state of the field, prompting investigators to begin collecting new data and addressing questions that have heretofore been impossible to answer about the ecology, evolution, and functional morphology of avian nectarivory. This article is protected by copyright. All rights reserved.
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Sexual reproduction of seed plants depends largely on pollen transfer. The pollination service provided by pollinators for wild plants and managed crops is one of the most crucial ecological processes on our planet, as it plays an essential role in sustaining biodiversity and crop production. Factors such as agricultural intensification, habitat fragmentation, and global climate change have increased the risk of pollinator decline and extinction, which would have detrimental effects on ecological function and agricultural production. To maintain the stability of ecological interactions between plants and pollinators, a series of pollinator monitoring schemes have been established, ranging from the regional to international scale. Participants including volunteer citizens and professional scientists have obtained the status and trends of pollination systems, thereby helping to provide early alerts and feedbacks for the risk of natural and agricultural ecological systems. In this view examining the methodologies of pollinator monitoring, we emphasize that it is necessary to distinguish pollinators from floral visitors. A diversity of direct and indirect methods for monitoring pollinators is summarized for seven types of animals (including Lepidoptera, Coleoptera, Hymenoptera, Diptera, Aves, Mammalia, and Lacertilia, respectively). A simple monitoring program that includes volunteer participation is also recommended. Commonly used field monitoring strategies for seven groups of pollinators would be useful as references for monitoring additional pollinator faunas. The pros and cons of these diverse methods for protecting and monitoring pollinators are discussed, which is useful for the long-term detection of pollinator dynamics.
In order to determine the effects of recent diet on prey choice, Senegalese chameleons (Chamaeleo senegalensis) were maintained on a diet consisting either of long-horned grasshoppers (Scudderia sp.) or of house crickets (Acheta domesticus). Choice tests showed that when the chameleons were being maintained on grasshoppers, their preferences for crickets became stronger over a period of days. Similarly, when the chameleons were being maintained on crickets, their preferences for grasshoppers became stronger over a period of days. These results show that prey preferences may become stronger for prey types that have not been included in the predator's recent diet. The results also suggest that nutrient constraints may be important in determining prey selection in insectivorous lizards.
The relationship between foraging behavior and resource availability for the long-nosed bat (Glossophaga soricina) and five species of plants it fed on in northern Columbia was investigated in a 10-mo study. Glossophaga employed two foraging tactics: (1) territorial defense of concentrated food sources, and (2) trapline foraging along regularly used feeding routes. The tactic used depended on availability of Agave desmettiana nectar and the individual bat's ability to dominate conspecifics. When both hunger and nectar levels were highest, bats concentrated their feeding activity on A. desmettiana. Aggressive behavior was displayed by dominant male and female bats during the first 3-5 h of feeding. Territorial behavior ceased suddenly when nectar levels were depleted by 50% or more at 2.5-5 h after sunset. Later in the evening, bats foraged briefly from one plant to another at several species along regularly used routes. Bats that maintained early-evening territories had increased access to nectar-rich agave flowers and had significantly smaller total foraging areas than nonterritorial bats. The feeding territories of female Glossophaga were shared with their immature offspring. Territorial behavior at agave was attributed in part to defensibility of its flowers. Foraging experiments demonstrated that G. soricina used a feeding strategy that was efficient with respect to choice of food patch and allocation of time. This is the first study that used marked individuals to document feeding territories and trapline foraging for nectar-feeding bats.
The nectar secreted by hummingbird-pollinated flowers is rich in sucrose, whereas nectar secreted by passerine-pollinated plants contains a mixture of glucose and fructose. To test the hypothesis that sugar preferences and nectar composition are correlated, I examined the sugar preferences of three species of Mexican hummingbirds (Amazilia rutila, Cynanthus latirostris, and Chlorostilbon canivetii). As predicted, the three species preferred sucrose over glucose, fructose, and a mixture of glucose and fructose (hexose mixture) in paired preference tests. Preferences for simple sugars were ranked as: sucrose > hexose mixture > glucose > fructose. The preference of hummingbirds for sucrose was not reversed by feeding hummingbirds a hexose mixture as a sole diet for 20 days. The preferences of hummingbirds for different sugars are puzzling because sucrose, glucose, and fructose have approximately the same energetic content. I hypothesized that sugar preferences were correlated with differences in the efficiency with which hummingbirds assimilated different sugars and/or in the time they required to process these sugars in the digestive system. Sucrose, glucose, and fructose, however, were assimilated by hummingbirds with equally high efficiency (>97%). Glucose solutions were processed by hummingbirds at a slower rate than hexose mixtures and sucrose solutions, and hence, were less profitable. Sucrose and hexose mixtures were processed at the same rate and therefore had the same profitability. Therefore, the preference of hummingbirds for sucrose over hexose mixtures cannot be explained by differences in assimilation efficiency or digestive handling time. Sucrose must be hydrolyzed into its monosaccharide components, glucose and fructose, before it can be absorbed in the intestine and used as an energy source. Relative to other birds, hummingbirds exhibit highly specialized digestive traits, such as very high rates of intestinal sucrose hydrolysis and glucose transport, which allow them to use sucrose as efficiently as mixtures of glucose and fructose. Many passerine species, in contrast, use the more easily absorbed monosaccharides, glucose and fructose, more efficiently than sucrose. The distribution of nectar sugars among bird-pollinated plants seems to be the result of the evolutionary response of plants to two sets of pollinators with different degrees of digestive specialization.