Do es territory quality and c haracteristics influence the frequency and length of spiral flights amongst different species of butterflies? Abstract Spiral flight conflicts between butterflies have been widely studie d , often investigating which individual s win , and why. Very little has been explored in terms of the frequency and intensity of these conflicts, and what influence territory characteristics have. This was measured in an observational study method, recording frequency and length of conflicts as well as territory characteristics such as lux and temperature. It was found that lux level, temperature and grass type significantly predict frequency and length of spiral flight conflicts. It was concluded that territory quality may have a large influence on the amount and intensity of these spiral flight conflicts b etween butterflies of different species , irrespective of who wins. Introduction Many species of male butterfly in the United Kingdom, including the C omma, Peacock, and S peckled W ood ( Pararge aegeria) butterfly reside in temperate woodlands in spots of sun , as this increases opportunities to find female mates (Davies, 1978). There are, however, more males than there are sunspots, leaving some butterflies patrolling for vacancies, and often intruding on sunspots that already have a resident male occupying th em (Davies, 1978; Scott, 1974; Stutt & Wilmer, 1998). As male butterflies are famously very territorial, this then leads to conflict between the resident male and the intruder, in an aerial, no - contact altercation called a ‘spiral flight’, over the ownersh ip of the sunspot territory (Davies, 1978; Kemp, 2000). These conflicts typically end with one butterfly retreating – the loser – and one butterfly returning to the sunspot to reside there – the winner (Davies, 1978; Stutt & Wil l mer, 1998). Many research ers have investigated this conflict over territory, mostly seeking to establish a pattern of who typically wins these altercations. In a widely cited paper by Davies (1978), it was suggested that the original resident of these sunspots always wins these conflicts, as simply an arbitrary convention all follow. However, this idea has been re - tested in multiple studies, and very widely co ntested by other researchers, causing debate on this phenomenon (e.g., Wickman & Wi klun d, 1983). For example, some pieces of subsequent research into this phenomenon have found that characteristics of the male butterflies involved may determine the outcome of these conflicts instead . Both Hardy (1998), and Stutt and Wil l mer (1998), found evidence to suggest that body temperature of the males involved may have a significant association with who wins. This was also found by Austad, Jones and Waser (1979), in which da ta implied that the resident males won these aerial contests due to the fact that they had been residing in sunspots and were therefore hotter , and won due to temperature - related ability rather than any sort of convention. In a similar way, some studies have suggested that the outcome of these disputes is determined simply by one male being a superior competitor than the other. For example, it has been inferred that the resident may win due to being a better competitor, as that could have been how they ac quired the sunspot in the first place (Leimar & Enquist, 1984). A review study by Kemp and Wi klun d (2001) also concluded that the most likely reason why residents win is due to them being more capable fighters – ones that feel the cost of the fight relativ ely slowly during the process compared to their competitor. Echoing these findings in a different way, Kemp (2000) also found that, when investigating the role of body size in triumph in spiral flights, body size does not matter but age meant that a butter fly was a superior competitor, leading to winning the contest, and being the resident of the sunspot. It has even been suggested that contact with a female may determine the outcome of a spiral flight – affecting motivation and leading a male to becom e dominant and reverse the outcome if they were losing (Bergman, Olofsson & Wiklund, 2010). It was concluded in this case that variation in intrinsic motivation translated to eagerness to take over the vacant territory, and variation in the value of the re source (sunspot) and differences in motivation are important for settling these conflicts in butterflies. This was also not the first study suggesting th at quality of resource, being the quality of the sunspot territory, may determine these spiral flight conf licts. In research by Baker (1972), it was found that encounters and spiral flight conflicts may vary in their intensity based on the value of the resource, i.e., the territory that they are contesting. Furthermore, in Stutt and Willmer (1998)’s research, in which it has been suggested that the temperature of the male influences the outcome of these contests, also suggests that this is due to territory quality. In their study, they indicate that warmer males are able to fly for longer and therefore are more likely to win th ese contests, and this is due to the resident basking in their sunspot while the other male is cooler from spending time patrolling. Following this logic, those with better sunspots – a higher quality territory – will have a higher temperature due to it being a better sunspot, subsequently leading to winning a territorial conflict. Based on this idea, and the fact that these previous studies have most (if not all) used experimental manipulations or staged procedu res to gain this evidence, this study aims to investigate the role of territory quality and habitat characteristics on the number and intensity of these spiral flight conflicts, between different species of woodland butterfly in different locations Due to the majority of these previous studies and findings being based on male Speckled Wood butterflies, and in experimental or only one woodland habitat, this study also aims to investigate whether species has an effect on number and intensity of this territor ial conflict , as well as grass type, tree cover and what the butterfly is perched on Very few studies have investigated what really happens in these conflicts, with butterflies allowed to stay in their natural context, a gap that this study aims to fill. Based on previous findings, it is hypothesised in the present study that habitat type , and territory quality – measured by lux level and temperature – and species of butterfly involved in the spiral flight conflict, will significantly predict the frequency and intensity (length) of these spiral flight contests. Method Location Butterflies were observed in four different locations in Exeter, UK , labelled one to four Location one was on the University of Exeter Streatham campus, on Birk’s Bank, located by Birk’s Grange Village (See Appendix A). Location two was also on the University of Exeter Streatham Campus, specifically the bank and Reed Pond by Reed Hall (See appe ndix B). The third location was situated by the river Exe , on the adjacent side of the river from Water Lane, along the field adjacent to the Pollinator Habitat (see Appendix C). The fourth location was Belle Isle Park , across the river Exe from the Trews Weir suspension bridge (see Appendix D). One day was spent in each of the University of Exeter Streatham campus locations, and two days were spent collecting data in the river Exe locations. Materials A lux meter was used to measure sunlight in each ter ritory a butterfly was found in, as well as a temperature reading being taken in the same spot using a temperature reading application on a smartphone (in degrees Celsius). A stopwatch was used to record the time (in seconds) that each spiral flight that was obse rved lasted for, and each spiral flight was tallied onto the count of total spiral flights seen at that particular location. The species of butterfly seen was also double - checked using an internet search engine on a smartphone , and th en noted down Procedure The University of Exeter locations on Streatham campus were each visited for one day, and the river Exe locations were each visited for two days. Once at the specific location, the area was scanned and observed until a butterfly was spotted, either resting, flying, or fighting. Once a butterfly was seen, it was observed for 20 minutes to investigate its behaviour. If a spiral flight conflict did not occur in this time, the lux , temperature, type of habitat, grass, perch it was on, and species were recorded, and researchers moved on to scan for any more butterflies nearby. This was to distinguish a ‘resting’ butterfly with one that is engaging in conflict or territorial behaviou r. If a spiral flight conflict occurred, as soon as the first spiral was sighted, a stopwatch was started in order to record the length of the spiral flight, stopping when the butterflies flew away from each other, and one did not return to the territory. Once the flight had ended, the lux, temperature, type of habitat, grass type and perch type (as well as butterfly species) were recorded in the territory in which the butterflies were originally, where one returned to after the conflict. Researchers then scanned for any additional butterflies in the area or waited until others appeared or fought in the area. All data was recorded on smartphones and written down in hard copy , and entered into a spreadsheet at the end of each day of research. Results Descr iptive statistics Prior to inferential analysis, m eans and standard deviations were calculated for dependent variables and some territory quality variables , in order to establish overall averages of spiral flight length, number of spiral flights, lux level, and temperature ( See Table 1). Table 1 - Means and Standard deviations for dependent and territory variables Variable Mean S tandard Deviation Spiral flight length Number of spiral flights Territory lux level Temperature of territory 14.54 6.79 49411.82 14.86 35.18 4.12 25017.85 1.89 As can be seen in the table above, it appears that the length of the average spiral flight is under thirty seconds (M = 14.54, SD = 35.18), and the average number of spiral flights seems to be under ten overall (M = 6.79, SD = 4.12). The average lux level in a territory is indicated to be under 50,000 lx (M = 49411.82, SD = 25017.85), and the average temperature of the territories measured appear to be close to fifteen degrees Celsius (M = 14.86, SD = 1.89). Inferential statistics Two multiple linear regression analyses were run in order to investigate the significance of territory quality characteristics of lux level and temperature, as well as habitat characteristics of tree cover, grass type, and perch type, and species of butterfly, in predi cting both length of spiral flight conflicts , and total number of spiral flight conflicts ( See Table s 2 and 3). Findings from the first multiple regression analysis found that a model comprised of lux level, temperature (Celsius), habitat type (tree cover age), grass type (cut or scrub), species of butterfly, and perch type ( g round, bramble, tree branch , bush or flower) , was not a significant predictor of length of spiral flight conflicts (in seconds) , R ² = 0.36, F ( 14,24) = 0.98, p = 0.50 Examination of plots suggest normal distribution of residuals with no outliers , and residual plots also indicated homoscedacity of variance also with no outliers A Durbin - Watson test suggested no significant autocorrelation of residuals ( p = 0.27) , sugges ting the assumption of independence is met All variance inflation factors were also below 2, indicating no multicollinearity between the predictors. Table 2 - Regression model coefficients for length of spiral flight conflicts Predictor Estimate Standard Error T P Intercept Lux level Temperature Habitat type – Tree cover Grass type Species (Holly Blue) Species (Orange tip) Species (Peacock) Species (Small Tortoiseshell ) Species (Small white) Species (Speckled wood) 5.71 8.98 - 8.25 4.55 - 2.34 - 1.45 7.15 4.37 1.56 3.09 1.35 6.26 3.70 4.08 4.01 1.83 3.40 3.73 3.24 3.11 3.27 2.85 0.91 2.43 - 2.03 1.13 - 0.13 - 0.43 0.19 0.14 0.50 0.001 0.47 0.37 0.02 0.05 0.27 0.90 0.67 0.85 0.89 0.62 1.00 0.64 Perch (Bush) Perch (Flower) Perch (Ground) Perch (Tree Branch) 1.25 - 1.29 2.45 1.20 4.50 2.45 1.91 1.88 0.28 - 0.53 1.28 0.64 0.78 0.60 0.21 0.53 As can be seen in Table 2 above, the two variables that were significant in predicting the length of spiral flight conflict s were lux level (t = 2.43, p = 0.02), and temperature (t = - 2.03, p = 0.05). No other variables were significant in predicting length of spiral flight conflicts , including species , habitat characteristics of grass type and tree cover, or perch type Findings from the second multiple regression analysis found th at a model comprised of lux level, temperature (Celsius), habitat type (tree coverage), grass type (cut or scrub), species of butterfly, and perch type (ground, bramble, tree branch, bush, or flower), was a significant predictor of total number of spiral f light conflicts, R ² = 0. 74 , F ( 14,24) = 4.86 , p < 0.01 . Examination of plots suggest normal distribution of residuals with no outliers, and residual plots also indicated homoscedacity of variance also with no outliers. A Durbin - Watson test suggested no significant autocorrelation of residuals ( p = 0. 71 ), suggesting the assumption of independence is met. All variance inflation factors were also below 2, indicating no multicollinearity between the predictors. Table 3 - Regression model coefficients for total number of spiral flight conflicts Predictor Estimate Standard Error T P Intercept Lux level Temperature Habitat type – Tree cover Grass type Species (Holly Blue) Species (Orange tip) Species (Peacock) Species (Small Tortoiseshell) Species (Small white) Species (Speckled wood) - 1.22 4.39 8.39 9.31 3.18 2.42 1.67 3.27 1.79 1.04 - 6.04 4.69 2.77 3.06 3.00 1.37 2.54 2.80 2.43 2.33 2.45 2.13 - 2.59 1.59 2.75 0.31 2.31 0.95 0.60 1.34 0.77 0.43 - 0.03 0.02 0.13 0.0 1 0.76 0 .03 0.35 0.56 0.19 0.45 0.67 0.98 Perch (Bush) Perch (Flower) Perch (Ground) Perch (Tree Branch) - 5.60 1.19 6.33 3.30 3.37 1.84 1.43 1.41 - 1.66 0.65 0.44 0.23 0. 11 0. 52 0.66 0.82 As can be seen in Table 3 above, the t wo variables that were significant in predicting the total number of spiral flight conflict s were temperature (t = 2. 75 , p = 0.0 1 ), and grass type (t = 2.31 , p = 0.0 3 ). No other variables were significant in predicting the total number of spiral flight conflicts, including lux level, species, habitat characteristics of grass type and tree cover, or perch type. Discussion The aim of this study was to establish whether habitat characteristics, such as grass type and tree cover, and territory quality, based on lux level and temperature , as well as specific species of woodland butterfly, have a predictive effect on frequency and intensity of spiral flight conflicts. It was hypothesised that habitat characteristics, territory quality and species would all have a significant influence on f requency and intensity (length) of spiral flight conflicts, based on previous literature. This was, however, not the case according to the findings of this study. Analysis suggests that only a few of these factors may be significant in predicting frequency and length of spiral flights, such as lux level, temperature, and grass type. The only significant factors found in predicting frequency of spiral flights were temperature of territory and grass type in the habitat. This only partially supports the idea that quality of territory and habitat characteristics may predict spiral flight conflicts, as only one factor of each was found to possibly predict the frequency of these contests. This could potentially indicate support for previous findings that territo ry quality, i.e., quality of the resource being held (the sunspot) , may produce an effect on the intensity of spiral flights (Baker, 1972) as it predicted the frequency of them in this study , but only in terms of temperature. This suggests that perhaps the quality of the sunspot territory may not include the level of sunlight, and the motivation behind defending the territory is its optimal temperature, irrespective of lux level. This c ould also be seen to support and further t he findings of Stutt and Wilmer ( 1998), as the temperature of the male, due to basking in the sunspot, was indicated to influence the outcome of these conflicts. This could be seen to be furthered in this study, adding the indication that the amount of spi ral flight conflicts that take place could be due to the temperature of the male, as a result of the sunspot temperature. The significance of grass type in the habitat is a finding that is unique to this study , indicating that the type of grass in a habitat may predict more spiral flight conflicts, which may or may not also relate to territory quality – suggesting perhaps a sunspot in a certain type of grass is more of an advantageous location than another type, but this would need to be studied further. In contrast, the characteristics that were significant in predicting the length of spiral flight conflicts were lux level – level of sunlight , and temperature. This does not match the significant predictors of frequency of these conflicts, suggesting that fre quency and intensity or escalation of spiral flights may have different driving forces motivating them. These particular findings suggest that the length, and therefore intensity or escalation of spiral flight conflicts once they have begun, is predicted by t he amount of sunlight and temperature in a sunspot. This indicates more support for the idea in previous studies that the quality of territory is a significant influence on the intensity of these conflicts (Baker, 1972) , as this was directly shown in th ese findings Furthermore, this also echoes the support for temperature influencing these conflicts (Stutt & Wilmer, 1998), as previously mentioned There were, however, no habitat characteristics significant in predicting the length of these conflicts, indic ating that habitat type – grass type and tree cover – does not influence the escalation or intensity of these spiral flights , but slightly influences the frequency of them. This has not previously been found in past research, so it appears that perhaps territory quality characteristics of sunlight level and temperature are the only driving forces of escalating these conflicts and them lasting longer. This may be due to the qu ality of the territory making the conflict more of an important one to win, due to the resource being more valuable – increasing motivation of both butterflies to continue the conflict and try to win, more so than lower quality territories. This could also mean that the difference in significance in sunlight level predicting intensity but not frequency of spiral flights, is due to sunspots with higher lux level being the location for longer spiral flights, but not necessarily more or less than other sunspot s , however, this would need to be established with subsequent study. From both analyses, it is indicated that species is not significant in predicting either frequency or intensity of spiral flights , suggesting that species do not differ significantly in t he nature of this conflict behaviour , though speckled woods have been much more frequently studied (e.g., Davies, 1978; Stutt & Wilmer, 1998; Wickman & Wiklund, 1983). Overall, t his study has furthered understanding of predictors of spiral flight frequency and intensity (length) across different species of butterfly and has contributed more knowledge on what actually happens during these conflicts, without experimental manipulation or staged contests, as is the case with most, if not all, previous studies o f these conflicts ( e.g ., Davies, 1978; Stutt & Wilmer, 1998; Wickman & Wiklund, 1983). However, there are limitations to observational study, with less control over extraneous variables and more difficulty in establishing the outcome of these contests with out marking individual butterflies , so conclusions that can be drawn from this study should be taken with such limitations. Future study could incorporate some elements of control, perhaps combining observational and experimental methods to yield more results It would also be useful for future studies to look further into the difference in influence of sunlight level in frequency and intensity of spiral flights, and in perhaps a wider range of habitat characteristics to establish whether there is really no large significant effect of them References Austad, S. N., Jones, W. T. and Waser, P. M. 1979. Territorial defence in speckled wood butterflies: why does the resident always win? Animal Behaviour 27, 960 - 961. Baker, R. R. ( 1972 ) . Territorial behaviour of the Nymphalid butterflies, Aglais urticae (L.) and Inachis io (L.). Journal of Animal Ecology , 41 , 453 - 469. Bergman, M., Olofsson, M., & Wiklund, C. (2010). Contest outcome in a territorial butterfly: the role of motivation. Proceedings. Biological sciences , 277 (1696), 3027 – 3033. https://doi.org/10.1098/rspb.2010.0646 Davies, N. B. (1978). Territorial defence in the speckled wood butterfly (Pararge aegeria): The resident always wins. Animal Behaviour, 26 (1), 138 – 147. https://doi.org/10.1016/0003 - 3472(78)90013 - 1 Hardy I. C. (1998). Butterfly battles: on conventional c ontests and hot property. Trends in ecology & evolution , 13 (10), 385 – 386. https://doi.org/10.1016/s0169 - 5347(98)01430 - x Kemp, D. J. ( 2000 ). Contest behavior in territorial male butterflies: does size matter? Behavioral Ecology , 11 , 591 - 596. Kemp, D., Wiklund, C. (2001). Fighting without weaponry: a review of male - male contest competition in butterflies. Behav ioural Ecol ogy and Sociobiol ogy, 49 , 429 – 442. https://doi.org/10.1007/s002650100318 Leimar, O. & Enquist, M. (1984). Effects of asymmetries in owner - intruder conflicts Journal of Theoretical Biology, 111 (3), 475 - 491. https://doi.org/10.1016/S0022 - 5193(84)80235 - 0 Scott, J. A. ( 1974 ) . Mate - locating behaviour of butterflies. The American Midland Naturalist , 91 , 103 - 117. Stutt, A . D. & Willmer, P. ( 1998 ) . Territorial defence in speckled wood butterflies: do the hottest males always win? Animal Behaviour , 55 , 1341 - 1347. Wickman, P. - O. & Wiklund, C. ( 1983 ) . Territorial defence and its seasonal decline in the speckled wood butterfly (Pararge aegeria). Animal Behaviour 31, 1206 - 1216. Appendices Appendix A – Map of location one for data collection Data collection area Appendix B – Map of Location two for data collection Data collection area Appendix C – Map of Location three for data collection Data collection area Appendix D – Map of Location four for data collection Data collection area