Nocturnal foraging and activity by diurnal lizards: Six species of day geckos (Phelsuma spp.) using the night-light niche

Abstract

Altered environments in urban areas are known to impact and change animal behaviour. In particular, artificial light at night (ALAN) affects behaviour across taxonomic groups, including reptiles. Geckos in the genus Phelsuma are predominantly diurnal, but some have been documented to alter their foraging behaviour from a diurnal to nocturnal activity period when they have access to artificial light sources. Herein, we report new observations of six Phelsuma spp. (Andaman day geckos, P. andamanensis; blue-tailed day geckos, P. cepedi-ana; Madagascar giant day geckos, P. grandis; Reunion ornate day geckos, P. inexpectata; gold dust day geckos, P. laticauda; Mahe day geckos, P. sundbergi longinsulae) using artificial lights to engage in nocturnal activity that includes foraging, courtship, and agonistic behaviour. Artificial light at night augments the amount of time predators, especially visual predators, can spend foraging. This can increase their overall daily activity period (i.e. the amount of time spent active within 24 h), and research is yet to fully understand the cost-benefit trade-offs this altered behaviour has on individual fitness. Overall, our novel accounts of six Phelsuma spp. contribute to knowledge regarding the diversity of animals that have altered their behaviour in response to ALAN and highlight the behavioural flexibility of this group of geckos.

Full text

Nocturnal foraging and activity by diurnal lizards: Six
species of day geckos (Phelsuma spp.) using the night-light
niche
JAMES BAXTER-GILBERT,
1
*CL

AUDIA BAIDER,
2
F.B. VINCENT FLORENS,
3
OLIVER HAWLITSCHEK,
4
ASHWINI V. MOHAN,
5
NITYA P. MOHANTY,
1
CARLA WAGENER,
1
KATHLEEN C. WEBSTER
6
AND JULIA L. RILEY
7,8
1
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Matieland,
South Africa (Email: jx_baxtergilbert@laurentian.ca);
2
The Mauritius Herbarium, Agricultural
Services, Ministry of Agro-Industry and Food Security, R
eduit (Email: cbaider@govmu.org);
3
Tropical
Island Biodiversity, Ecology and Conservation Pole of Research, Faculty of Science, University of
Mauritius, R
eduit, Mauritius (Email: vin.florens@uom.ac.mu);
4
Centrum f€
ur Naturkunde, Universit€
at
Hamburg, Hamburg;
5
Department of Evolutionary Biology, Zoological Institute, Braunschweig
University of Technology, Braunschweig;
6
Zoologische Staatssammlung M€
unchen (ZSM-SNSB),
Munich, Germany;
7
Department of Botany and Zoology, Stellenbosch University, Matieland, South
Africa; and
8
Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
Abstract Altered environments in urban areas are known to impact and change animal behaviour. In particu-
lar, artificial light at night (ALAN) affects behaviour across taxonomic groups, including reptiles. Geckos in the
genus Phelsuma are predominantly diurnal, but some have been documented to alter their foraging behaviour
from a diurnal to nocturnal activity period when they have access to artificial light sources. Herein, we report
new observations of six Phelsuma spp. (Andaman day geckos, P.andamanensis; blue-tailed day geckos, P.cepedi-
ana; Madagascar giant day geckos, P.grandis;R

eunion ornate day geckos, P. inexpectata; gold dust day geckos,
P.laticauda; Mah
e day geckos, P.sundbergi longinsulae) using artificial lights to engage in nocturnal activity that
includes foraging, courtship, and agonistic behaviour. Artificial light at night augments the amount of time
predators, especially visual predators, can spend foraging. This can increase their overall daily activity period
(i.e. the amount of time spent active within 24 h), and research is yet to fully understand the cost–benefit trade-
offs this altered behaviour has on individual fitness. Overall, our novel accounts of six Phelsuma spp. contribute
to knowledge regarding the diversity of animals that have altered their behaviour in response to ALAN and high-
light the behavioural flexibility of this group of geckos.
Key words: artificial light at night, behavioural shift, biological invasions, flexibility, foraging, reptile, urban.
NATURAL HISTORY NOTE
Anthropogenic landscapes are known to dramatically
alter animal behaviour, including changes in beha-
vioural traits (e.g. boldness and exploration), habitat
use, and foraging, which relates to both the chal-
lenges and opportunities present in human-altered
environments (Lowry et al. 2013). Notably, artificial
light at night (ALAN) affects reptiles in several ways,
including changes in antipredator behaviours, dis-
rupted navigation, and altering ecological and indi-
vidual interactions by centralising invertebrate prey
(Perry et al. 2008). One of the impacts easiest to
recognise is when diurnally active species increase
nocturnal activity to exploit feeding opportunities
around lights (i.e. within the ‘night-light niche’; Gar-
ber 1978; Perry et al. 2008). Previous research has
reported more than 40 diurnal reptile species using
this night-light niche for foraging (Deso 2007; Perry
et al. 2008; Maurer et al. 2019; Dubos et al. 2020)
with the list growing annually. These accounts
include three species of day gecko: R
eunion ornate
day geckos (Phelsuma inexpectata, introduced popula-
tion), gold dust day geckos (P.laticauda, invasive
Hawaiian population), and Koch’s giant day geckos
(P.kochi; native population; Garc

ıa & Vences 2002;
Perry & Fisher 2006; Dubos et al. 2020). Here we
report new observations of six day geckos using the
night-light niche to engage in nocturnal activity: (i)
Andaman day gecko (P.andamanensis, native popula-
tion), (ii) blue-tailed day geckos (P.cepediana, native
*Corresponding author. Centre for Invasion Biology, Depart-
ment of Botany and Zoology, Natural Sciences Building, Pri-
vate Bag X1, University of Stellenbosch, Matieland, Western
Cape 7602, South Africa.
Accepted for publication January 2021.
© 2021 Ecological Society of Australia doi:10.1111/aec.13012
Austral Ecology (2021) ,–

population), (iii) Madagascar giant day geckos
(P.grandis, invasive population), (iv) R
eunion ornate
day geckos (P. inexpectata, native population), (v)
gold dust day geckos (P. laticauda, invasive popula-
tion), and (vi) Mah
e day gecko (P.sundbergi longinsu-
lae, native population). These observations were
made by different authors over many years of work-
ing in the Mascarenes, Comoros, Andamans and
Seychelles archipelagos.
Andaman day gecko, Phelsuma andamanensis
Blyth, 1861
Andaman day geckos are medium-sized diurnal gekko-
nids (maximum snout–vent length (SVL) 57 mm,
AVM unpublished) endemic to the Andaman archipe-
lago. On 19 November 2016 (sunset at 16:48 h),
between 19:00 and 22:00 h, we captured a juvenile
that was foraging alongside invasive Asian house
geckos (Hemidactylus frenatus) and common four-
clawed geckos (Gehyra mutilata) inside a building on
walls close to a white light source (bulb type unknown;
incandescent or LED). This observation was made in
Chainpur Village, Middle Andaman Island
(12.7418°N, 92.8048°E). Another observation of
Andaman day geckos nocturnally foraging was made
on 14 March 2017 (sunset at 17:28 h), between
19:00–22:00 h, in Mount Harriet National Park
(11.7204°N, 92.7337°E). Like the previous observa-
tion, this was observed inside a cabin with a white light
source (bulb type unknown; incandescent or LED).
Blue-tailed day gecko, Phelsuma cepediana
Milbert, 1812
Blue-tailed day geckos are medium-sized diurnal gek-
konids (maximum SVL 58 mm; Rocha et al. 2010)
that are endemic to the Mascarene archipelago. At
20:15 h on 11 July 2019 (sunset at 17:45 h), we
observed a blue-tailed day gecko foraging around a
white, fluorescent light source (i.e. a tube light;
Fig. 1) in the village of Notre Dame on Mauritius
(20.1397°S, 57.5618°E). At this time, most insects
found around the lights were moths, flying ants, and
beetles, and on several occasions, these geckos cap-
tured prey. Over the previous fortnight, we had made
several undocumented observations of these geckos
feeding around the same outdoor lights nightly, sug-
gesting this was not a once-off event. We were able
to distinguish between individuals due to tail damage
and determine that at least two individuals were feed-
ing around this light source. During these observa-
tions, we also noted several invasive Asian house
geckos foraging around the same lights; however, no
physical heterospecific interactions were observed
(e.g. biting, fighting, chasing, or following). Addi-
tionally, during the early 2000s, we also observed
hatchling, juvenile, and adult blue-tailed day geckos
active on the walls in the early evenings (~20:00–
21:30 h) inside a residence in Vacoas, Mauritius,
illuminated with a white, incandescent light source.
Additionally, we saw an adult foraging on ants and
moths at 22:45 h above a white, incandescent light
source on an outside wall at the same location on 14
November 2020 (sunset at 18:26 h).
Madagascar giant day gecko, Phelsuma grandis
Gray, 1870
Madagascar giant day geckos are large diurnal gekko-
nids (maximum SVL 102.4 mm; Rocha et al. 2010)
native to Madagascar and invasive on the Mascarene
archipelago where these observations were made.
During March and August of 2016, we observed
many individuals feeding in urban areas near artificial
lights in Mauritius. One specific example of this
occurred on the evening of 3 March 2016 (sunset at
18:34 h), when various individuals were foraging
around white, fluorescent light sources for insects on
the hotel walls and in the restaurant area of Les Lata-
niers Bleus, Tamarin (20.3483°S, 57.3634°E)
between 19:00 and 21:00 h. In 2018, we also saw
this species foraging for insects shortly after dark
(~20:00 h) near a white, incandescent light source in
Vacoas, Mauritius.
R
eunion ornate day gecko, Phelsuma
inexpectata Gray, 1825
R
eunion ornate day geckos are medium-sized diurnal
gekkonids (maximum SVL 58 mm; Rocha et al.
Fig. 1. A blue-tailed day gecko (Phelsuma cepediana) verti-
cally perched below a 91 cm white, fluorescent light source,
nocturnally foraging for insects in Notre Dame, Mauritius.
Photo credited to JLR.
doi:10.1111/aec.13012 © 2021 Ecological Society of Australia
2 J. BAXTER-GILBERT ET AL.

2010) endemic to R
eunion. Between 10 and 16 July
2015 (sunset at 17:52 h) in Manapany-Les-Bains,
R
eunion (21.3737°S, 55.5887°E), we observed one
to two individuals active around a white, fluorescent
light source at night (18:30–20:00 h; Fig. 2). The
animals actively positioned themselves under the
light, suggesting their preference for the night-light
niche. Since this light was inside a bathroom, there
were very few insects, and no predation events were
observed. Yet, they would remain beside the light
while it was illuminated and exhibited behaviours
normally associated with daytime activity (e.g. court-
ship; Fig. 2c). Previous records note this species
feeding on moths near the artificial lights in the city
of Le Tampon, R
eunion, where a small, introduced
population occurs (Deso 2007). However, we here
report the first nocturnal behaviour within the spe-
cies’native distribution (Sanchez & Probst 2011).
Gold dust day gecko, Phelsuma laticauda
Boettger, 1880
Gold dust day geckos are medium-sized diurnal gek-
konids (maximum SVL 58 mm; Rocha et al. 2010),
which are native to northern Madagascar but occur
extensively as introduced species in tropical regions
throughout the Indian and Pacific Oceans. At
23:46 h on 19 March 2019 (sunset at 18:11 h), an
individual was observed foraging and successfully
capturing an ant (Fig. 3) near an amber, incandes-
cent light source on the wall of a resort near Mt.
Combani on Mayotte (12.8071°S, 45.1534°E) adja-
cent to degraded forest habitat. On the same night,
we also observed a gold dust day gecko interacting
with a flathead leaf-toed gecko (Hemidactylus platy-
cephalus)–a nocturnal gekkonid also introduced to
Mayotte –around the amber, incandescent light. The
two species lunged aggressively at one another when
in close contact during foraging. Despite the consid-
erably larger size of the flathead leaf-toed gecko, it
did not attempt to eat the day gecko. Interspecific
interactions like these were also documented in
Hawai’i, where gold dust day geckos, Asian house
geckos, and green anoles (Anolis carolinensis) were
foraging at the same night-light source (Perry &
Fisher 2006). Nocturnal foraging behaviour was pre-
viously recorded for this species, but mostly from
highly urbanised locations (e.g. in the capital city of
Mamoudzou; Dubos et al. 2020). This account
demonstrates this behaviour occurs in more natural
areas as well.
Mah
e day gecko, Phelsuma sundbergi
longinsulae Rendahl, 1939
Mah
e day geckos are medium-sized diurnal gekko-
nids (maximum SVL 65 mm; Rocha et al. 2010)
endemic to Seychelles. On 14 March 2017 (sunset at
18:31 h), between 19:00 and 22:00 h, we docu-
mented nocturnal activity of Mah
e day geckos at a
white, fluorescent light source near Anse Takamaka
(4.7790°S, 55.5000°E) on Mah
e Island (Fig. 4).
Fig. 2. R
eunion ornate day geckos (Phelsuma inexpectata) engaging in nocturnal activity under a white, fluorescent light
source inside a bathroom in Manapany-Les-Bains, R
eunion (a,b). This observation included courtship behaviour between
conspecifics (c). Photos credited to CB and FBVF.
© 2021 Ecological Society of Australia doi:10.1111/aec.13012
NIGHT-ACTIVE DAY GECKOS 3

These geckos were foraging for insects that were
attracted to this artificial light. Other nocturnal
geckos, tentatively identified as invasive Asian house
geckos, were also present at the same light source;
however, no physical interactions between any of
these geckos were observed.
DISCUSSION
Geckos of the genus Phelsuma are predominantly diur-
nal, except for the now-extinct Rodrigues giant day
gecko (P.gigas; Cheke & Hume 2008) and the extant
G€
unther’s day gecko (P.guentheri, Gerner 2008). Phel-
suma spp. are typically visual foragers, using colour
cues to detect and assess resources (Hansen et al.
2006). The night-light niche and ALAN environments
augment the amount of time visual predators can
spend foraging, thereby increasing the duration of their
overall activity time. However, such alterations to the
sleep-wake cycle may negatively affect individual fit-
ness (Aulsebrook et al. 2018).
Phelsuma spp. feed heavily on fruit, floral nectar,
pollen, and insects (Staub 1988; Nyhagen et al.
2001) and are important pollinators and seed dis-
persers in island ecosystems (Nyhagen et al. 2001;
Olesen & Valido 2003; Hansen et al. 2007; Hansen
&M
€
uller 2009; but see Bissessur et al. 2019).
Anthropogenic factors have previously been seen to
alter day gecko diets (Gardner & Jasper 2015), and
the reported nocturnal foraging on light-attracted
insects we present here could augment and/or alter
their nutritional intake, at least in urban areas. For
example, urban-dwelling Malagasy day geckos
(P. modesta leiogaster) feed heavily on anthropogenic
sugar-rich foods, with foraging on insects being gen-
erally rare despite an abundant availability (Gardner
& Jasper 2015). This behavioural and dietary plastic-
ity may predispose Phelsuma spp. to rapidly adjust to
anthropogenic areas (Gardner & Jasper 2015). Such
flexibility could also potentially increase the invasion
success of Phelsuma spp., the epicentres of which are
generally urban areas (Gaertner et al. 2017).
Our accounts of six Phelsuma spp. engaging in noc-
turnal activity contribute to the growing knowledge
of impacts ALAN may have on herpetofauna and
underscores the behavioural flexibility of these
geckos. We recommend that future research exami-
nes the individual repeatability of this behaviour to
determine if it is consistent over time, if it is more
prevalent within invasive populations compared to
Fig. 3. A gold dust day gecko (Phelsuma laticuada) hand
captured after successfully hunting an ant (Formicidae)
near an amber, incandescent light source on a small build-
ing near Mt. Combani, Mayotte. Photo credited to KCW.
Fig. 4. (a) Mah
e day geckos (Phelsuma sundbergi longinsu-
lae) active at night on the wall of a building near a white,
fluorescent light source in Mah
e Island, Seychelles. The
grey gecko associated with them is likely an Asian house
gecko (Hemidactylus frenatus). (b) A close-up of the Mah
e
day gecko (P. sundbergi longinsulae) active at night. Photos
credited to OH.
doi:10.1111/aec.13012 © 2021 Ecological Society of Australia
4 J. BAXTER-GILBERT ET AL.

ones from a species’native range, and if there are
secondary impacts on plant communities that rely on
certain Phelsuma spp. for pollination and seed disper-
sal. Overall, our observations suggest that there is a
wealth of research potential surrounding the biologi-
cal strategies employed by these enigmatic lizards to
thrive regardless of environmental change –whether
via urbanisation or biological invasions.
ACKNOWLEDGEMENTS
We would like to thank the DSI-NRF Centre for Excel-
lence in Invasion Biology, the Centre for Collaboration
in Africa at Stellenbosch University, the University of
Mauritius, and Prof. John Measey for their support. We
would also like to thank the staff of the National Parks
and Conservation Service in Mauritius and the Depart-
ment of Environment and Forests of the Andaman and
Nicobar Islands and the three reviewers whose sugges-
tions improved the manuscript.
CONFLICT OF INTEREST
The authors state they have no conflicts of interest
with respect to this article or its content.
AUTHOR CONTRIBUTIONS
James Baxter-Gilbert: Investigation (equal); Writ-
ing-original draft (lead); Writing-review & editing
(equal). Cl
audia Baider: Investigation (equal);
Writing-original draft (equal); Writing-review & edit-
ing (equal). Vincent Florens: Investigation (equal);
Writing-original draft (equal); Writing-review & edit-
ing (equal). Oliver Hawlitschek: Investigation
(equal); Writing-original draft (equal); Writing-review
& editing (equal). Ashwini V. Mohan: Investigation
(equal); Writing-original draft (equal); Writing-review
& editing (equal). Nitya P. Mohanty: Investigation
(equal); Writing-original draft (equal); Writing-review
& editing (equal). Carla Wagener: Investigation
(equal); Writing-original draft (equal); Writing-review
& editing (equal). Kathleen C. Webster: Investiga-
tion (equal); Writing-original draft (equal); Writing-
review & editing (equal). Julia Riley: Investigation
(equal); Supervision (lead); Writing-original draft
(equal); Writing-review & editing (equal).
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