Effects of Microhabitat Temperature on Escape Behavior in the Diurnal Gecko, Gonatodes…

dominguez-lopez_etal_Gonatodes_albigularis_flight_behavior_HerPeToZoa.qxd 28.07.2015 15:01 seite 1

HerPeToZoa 28 (1/2): 49 - 54 49 wien, 30. Juli 2015

effects of microhabitat temperature on escape behavior in the diurnal gecko, Gonatodes albogularis (duMéril & b ribon , 1836) (squamata: sauria: sphaerodactylidae )

die wirkung der Mikrohabitat-Temperatur auf das fluchtverhalten des tagaktiven Geckos Gonatodes albogularis (duMéril & b ribon , 1836) (squamata: sauria: sphaerodactylidae )

Moisés e. d oMínGueZ -l óPeZ & f ederiCo P. k aColiris & Á nGela M. o rTeGa -l eón

kurZfassunG die vorliegende arbeit untersuchte die wirkung der lufttemperatur auf das fluchtverhalten von Gonatodes albogularis (duMéril & b ribon , 1836) in einem tropischen Trockenwald-relikt kolumbiens. die ergebnisse zeigten negative korrelationen zwischen der Mikrohabitat-lufttemperatur und dem abstand zwischen echse und beutegreifer zum Zeitpunkt, zu dem die flucht ausgelöst wird sowie zwischen der Mikrohabitat-lufttemperatur und dem abstand der echse zum nächstgelegenen unterschlupf zum Zeitpunkt ihrer erstbeobachtung.

absTraCT The present study examined the effect of microhabitat air temperature on the escape behavior of Gonatodes albogularis (duMéril & b ribon , 1836) in a tropical dry forest relict of Colombia, south america. results showed negative correlation between both microhabitat air temperature and distance between lizards and predators at the moment in which escape is triggered and between temperature and distance of lizards to the closest shelter. keYwords reptilia: squamata: sauria: sphaerodactylidae: Gonatodes albogularis ; ecology, behavior, temperature; ectotherms; predation; Colombia

inTroduCTion

The escape behavior of ectotherm ani - distance is large, the risk of being preyed is mals is strongly affected by the variables low and escape should start delayed, because complexity of the microhabitat ( Gifford et the cost of unnecessary flight would nega - al. 2008; PenninGs 1990), body size ( Mar- tively influence the energy balance of the Tín et al. 2005) and ambient temperature individual and, consequently, its fitness. (CooPer 2000). among these factors, ambi - since reptiles are ectothermic verte - ent temperature takes a leading role because brates, the physiological and biochemical it is strongly linked to body temperature and, processes associated with their behavior therefore, to escape ability. optimal escape depend on the ambient and finally body theory explains the balance between the temperature ( barTHoloMew 1982; H ueY energy costs of escape and the risk of being 1982; a nGilleTTa et al . 2002; s eebaCHer preyed ( YdenberG & d ill 1986; C ooPer & 2005 ). The effect of the ambient air tem - frederiCk 2007). This balance determines perature on escape behavior is more impor - the moment of escape. if the distance be - tant in smaller reptiles, such as geckos tween prey and approaching predator is which are exposed to a great number of short, the risk of being preyed is high and potential predator species ( Greene 1988; escape should start hastily. However, if this MarTín 2002). several studies in lizards dominguez-lopez_etal_Gonatodes_albigularis_flight_behavior_HerPeToZoa.qxd 28.07.2015 15:01 seite 2

50 M. e. d oMínGueZ -l óPeZ & f. P. k aColiris & Á. M. o rTeGa -l eón

analyzed the relationship between air tem - shows a remarkable sexual dimorphism, perature and the predators’ approach dis - males having orange or yellow heads and tance ( CooPer 2000; b raun et al. 2010). in dun-colored bodies, whereas females are accordance with the optimal escape theory, more cryptic with a gray and brown color they found a negative correlation between pattern ( ellinGson 1994 ). some studies approach distance and temperature that can reported territorial behavior in this species be explained by the fact that small reptiles (bo HórqueZ et al. 2010). natural predators can run faster at higher temperatures and for of this gecko are larger lizards, snakes, this reason they can allow closer approxima - mammals, and birds ( fiTCH 1973; b ello tion of predators. if predators were not to 2000). attack, individuals would avoid the cost of The present study analyzed two essen - escape. However, when temperatures are tial components of the escape behavior of G. low, ectotherm animals of prey are slow and albogularis in relation to ambient air tem - cannot allow predators to approach too close perature. as was already demonstrated for without accepting a decrease in flight suc - other lizard species, hypothesis (# i) as - cess. in addition, lizards developed various sumes that individuals allow a closer alternative strategies to avoid predation such approach of potential predators at higher as crypsis, perching close to a shelter, or cau - ambient air temperatures. This hypothesis dal autotomy ( CooPer 2000; G aldino et al . predicts negative correlation between ap- 2006; s TankowiCH & b luM sTein 2005 ). proach distance and temperature. Hypothe- Gonatodes albogularis (duMeril & sis (# ii) assumes that the distance of indi - bribon , 1836) is a small diurnal sphaero - viduals to shelters varies as a function of air dactylid gecko that inhabits coastal habitats temperature. This hypothesis predicts posi - in south america to heights of 1,500 m a.s.l. tive correlation between ambient air temper - (rivero -b lanCo 1979; s CHarGel 2008). ature and distance between G. albogularis This gecko is common on tree trunks, in individuals and shelters. in addition, sex- crevices on the ground, on rocks and, less related differences in the escape behavior of frequently, on leaf litter on the ground. it this species were studied.

MaTerials and MeTHods

study area.— fieldwork was car - one of the observers. after that, one observ - ried out in one of the last relicts of tropical er (always the same) imitated a predator by forest located in the south of the Córdoba walking slowly and at constant speed of department, Colombia, south america about 1m/s in the direction of the detected (08°34’48.7” n, 75°42’28.4” w). This site individual until escape was triggered. in is part of the Choco-Magdalena region, each case, the following spatial variables characterized as dry Tropical forest, with (linear distances in meters) were recorded mean annual temperature of 28 °C and sea - following bauwens & T Hoen (1981) and sonal rains ( HernandeZ -C aMaCHo et al. vanHooYdonCk et al . (2007) : (a) approach 1992). distance (ad): distance between the lizard surveys.— fieldwork was done in and the observer at the moment when March and april, 2012, coinciding with the escape started; (b) running distance (rd): species’ period of high activity ( serrano - distance between the first location of the CardoZo et al. 2007). in search of the lizard and its location at first stop after geckos, two observers walked jointly along escaping; (c) end distance (ed): distance two parallel line transects (10 m apart, each between the observer and the point at which 10 m wide, 2 km long, sampling effort 326 the lizard stopped moving or the point at person hours), from 09:00 a. m. to 17:00 p. which the lizard went into hiding, and; (d) m. when an individual was found, the ob - distance to the closest shelter (dCs): dis - servers waited until the lizard showed by tance between the first location of the lizard moving its head or tail or by other behav - and the closest shelter (crevices on the ioral displays that it had detected at least ground, rocks, trunks or leaf litter on the dominguez-lopez_etal_Gonatodes_albigularis_flight_behavior_HerPeToZoa.qxd 28.07.2015 15:01 seite 3

effects of microhabitat temperature on the escape behavior in Gonatodes albogularis 51

Table 1: arithmetic mean value, standard deviation (sd) and range of the analyzed variables MT – micro - habitat air temperature; ad – approach distance; rd – running distance; ed – end distance and dCs – distance to the closest shelter. for definitions see Materials and Methods. Tab 1: Mittelwert, standardabweichung (sd) und spannweite der untersuchten variablen MT – Mikro- habitat-lufttemperatur, ad – entfernung zwischen Gecko und beobachter zu fluchtbeginn, rd – entfernung zwischen der stelle der ersten beobachtung des Geckos und seinem ersten Halt nach der flucht, ed – entfernung zwischen beobachter und der stelle an der der Gecko seine flucht beendete bzw. sich verkroch und dCs – entfernung von der stelle der ersten beobachtung des Geckos zum nächstgelegenen unterschlupf.

MT (°C) ad (m) rd (m) ed (m) dCs (m) arithmetic mean / Mittelwert 30.57 2.26 0.36 3.96 0.64 sd 1.70 0.81 0.11 14.47 0.35 range / spannweite 27 - 34 0.30 - 4.5 0.12 - 0.63 0.10 - 1.40 0.10 - 2.2

ground). all measurements were done an accuracy of 0.01 °C at the locations of using a tape measure with 1 cm accuracy. the individuals’ fist detection. as soon as the escape variables were meas - statistical analysis.— for ured, the individual was captured and the each variable, a two-sample randomization following data recorded (i) sex, on the basis test was used to compare the data of males of external features; (ii) age, classified as and females. The effect of microhabitat adult and juvenile on the basis of the mini - temperature on escape behavior was evalu - mum size at sexual maturity (30.1 mm for ated by simple randomization correlation males and 31.7 mm for females; serrano - tests between temperature (as the independ - CardoZo et al. 2007), and (iii) snout-vent ent variable) and ad, rd, ed and dCs (as length and tail length, using calipers with the dependent variables), for all individuals. 0.1 mm accuracy. individuals were released in those cases in which differences between at their original sites to avoid pseudorepli - males and females were observed, separate cation within transects. To exclude ontoge - correlation tests were run for each sex. all netic bias, only adult individuals were con - the analyses were performed using the null sidered in this study. test statistics with 10,000 permutations of The microhabitat air temperatures the software package rundom Pro 3.14 (MT) were taken at 1 cm above the surface (JadwisZCZak 2009). structure where the gecko was perched, with

resulTs

escape behavior data was recorded for = -0.89, p < 0.01; fig. 1) and between MT a total of 137 adult gecko specimens, 58 and dCs (randomization test: r = -0.67, p < females and 79 males. Table 1 presents the 0.01; fig. 2), whereas the variables rd mean values for the variables assessed. (randomization test: r = 0.16, p = 0.06) and Comparison of male versus female ed (randomization test: r = 0.03, p = 0.75) mean values of behavioral variables showed did not show any relationship with tempera - significant differences in ad, rd and ed ture. (randomization test: p < 0.01 in all cases; different from the above combined see mean values on Table 1) but not in dCs test result, sex-specific correlation tests (randomization test: p = 0.49). between MT and rd showed an effect of analysis of the correlation between microhabitat temperature on the running microhabitat temperature (MT) and behav - distance (rd) for males (randomization ioral variables (ad, rd, ed and dCs), test: r = 0. 33; p < 0.01), whereas for using the combined data of both males and females, no such effect was observed (ran - females, showed a negative relationship domization test: r = 0.07, p = 0.60). between MT and ad (randomization test: r dominguez-lopez_etal_Gonatodes_albigularis_flight_behavior_HerPeToZoa.qxd 28.07.2015 15:01 seite 4

52 M. e. d oMínGueZ -l óPeZ & f. P. k aColiris & Á. M. o rTeGa -l eón

fig. 1: relation between ad (m) and MT (°C) for fig. 2: relation between MT (°C) and dCs (m) for 137 specimens of Gonatodes albogularis (duMéril 137 specimens of Gonatodes albogularis (duMéril & & b ribon , 1836) studied. The distance between bribon , 1836) studied. The distance between the first lizard and observer (potential predator) at the location of the gecko and the closest shelter increased moment when escape started decreased with decreasing air temperature of the microhabitat. with increasing microhabitat temperature. abb. 2: Zusammenhang zwischen MT (°C) und abb. 1: Zusammenhang zwischen ad (m) und MT dCs (m) für 137 untersuchte individuen von (°C) für 137 untersuchte individuen von Gonatodes Gonatodes albogularis (duMéril & b ribon , 1836). albogularis (duMéril & b ribon , 1836). die entfernung von der stelle der ersten Mit steigender lufttemperatur nahm jene entfernung beobachtung des Geckos zum nächstgelegenen zwischen Gecko und beobachter (potentiellem unterschlupf nahm mit sinkender Mikrohabitat- freßfeind) ab, bei der die flucht einsetzte. Temperatur zu.

disCussion

The results support the optimal escape behavior of these geckos. not to overheat theory of YdenberG & d ill (1986). The and to maintain the preferred body tempera - negative relationship observed between ture under hot weather conditions, perching microhabitat temperature and approach dis - close to a shelter, including a regular retreat, tance suggests that, at higher temperatures, could be a successful strategy and, in addi - individuals allow their predators to get clos - tion, would minimize predation risk. er. This pattern is consistent with the fact another explanation could be related to the that lizards are more active at higher temper - territorial behavior displayed by this species atures, which is equivalent to an augmenta - (boHórqueZ et al. 2010). by perching close tion of agility, faster movements and, conse - to a shelter, irrespective of the ambient tem - quently, increased chance to escape. de - perature, lizards could more efficiently pro - laying its escape, the lizard would minimize tect their shelter from being used by com - the costs of an unnecessary spurt, thereby petitors. The observed negative relationship increasing its fitness. However, these con - between MT and dCs also means that the siderations are not universally valid for ani - distance to the closest shelter increases with mals, considering that several species that decreasing air temperature. Thus the gecko have high energy costs of locomotion, allow seems to accept the consequences of both the a closer approach when cool, relying on long distance to the shelter and reduced crypsis ( sTankowiCH & b luMsTein 2005). escape speed. This result is difficult to inter - The present study revealed a negative pret and additional studies are required to relationship between ambient air tempera - better understand the consequences of this ture and distance to closest shelter. This pat - behavior in G. albogularis . tern is not consistent with a strategy aiming in small ectotherms, when body tem - on the reduction of predation risk, but can be perature is low, escape may not be the most interpreted as thermoregulatory or territorial effective anti-predator behavior and alterna - dominguez-lopez_etal_Gonatodes_albigularis_flight_behavior_HerPeToZoa.qxd 28.07.2015 15:01 seite 5

effects of microhabitat temperature on the escape behavior in Gonatodes albogularis 53

tive strategies developed such as tail autoto - compensate for the costs of an extended my, discharge of chemical substances, and escape, not only in terms of expended ener - crypsis ( roCHa 1993). another alternative gy, but also time allocated for other activi - strategy is the selection of microhabitats ties, e.g., reproduction, foraging and ther - that provide good and safe shelters. How- moregulation. ever, ectothermic organisms also must con - Hence, the patterns observed in G. al- sider thermoregulatory requirements be - bogularis could be indicative of the avail - sides the benefits of shelters. for this rea - ability of an optimal microhabitat that pro - son, optimum microhabitats for lizards such vides adequate infrastructural requisites for as geckos would provide access to shelters, thermoregulating, protecting a territory and sites for thermoregulatory activities but also avoiding predators. food and mates. such optimal sites might

aCknowledGMenTs

This work was supported by the project mentos de bosque seco y zonas urbanas del departa - “Caracterización de aspectos ecológicos y conductu- mento de Córdoba” funded by “Grupo de investigación ales de especies comunes de anfibios y reptiles en frag - en biodiversidad”.

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daTe of subMission: January 3, 2014 Corresponding editor: Heinz Grillitsch

auTHors: Moisés e. doMínGueZ -l óPeZ (corresponding author < [email protected] >) - Grupo de investigación en biodiversidad, universidad de Córdoba, Colombia. Carrera 6 no. 76-103, Córdoba, Colombia; federico P. kaColiris - sección Herpetología, departamento de vertebrados, Museo de la Plata, Paseo del bosque s/n, la Plata (1900), buenos aires, argentina. Consejo nacional de investigaciones Científicas y Técnicas (ConiCeT), argentina < [email protected] >; Ángela M. orTeGa -l eón – Grupo de investigación en biodiversidad, universidad de Córdoba, Colombia. Carrera 6 no. 76-103, Córdoba, Colombia < [email protected] >.