Introduction
Several lizard species inhabit the University of Arizona’s Joseph Wood Krutch Gardens and interact with their environment in different ways. One such way is thermoregulation, which is influenced by body size and environmental temperature. Lizards are ectotherms, meaning they do not self-maintain internal body temperatures; instead, they are the same temperature as the surrounding environment. A rule that explains body mass and temperature correlations, called Bergmann’s rule, predicts a positive correlation between animal body mass and elevation. At higher elevations temperatures are lower, so this rule predicts that larger animals live in cooler environments (Pincheira-Donoso et al, 2008). However, Bergmann’s rule has only been shown in mammals and birds, but not necessarily for reptiles (Ashton e al, 2003). Only about 75 percent of ectotherms conform to Bergmann’s rule, however this number is under scrutiny and is believed to be lower (Pincheira-Donoso et al, 2008). In other cases, scaled reptiles known as squamates have reversed Bergmann’s clines, meaning the opposite of the rule is true because they are efficient at regulating their body temperatures by exhibiting specific behaviors (Sears 2004). Based on this interesting concept of whether ectotherms, or lizards specifically, exhibit Bergmann’s rule, a new study was formed with the following question: Do certain species of lizards prefer to occupy the space around velvet mesquite-1 (Prosopis velutina) and parry’s agave-2 (Agave parryi) during different times of the day in Krutch gardens? It is predicted if it’s a different time of day, such as morning hours versus evening hours, then there will be different lizard species visiting the area surrounding the two indicated plants. If it is a cooler temperature in the early morning or late evening, then either no lizards or only larger species of lizards will be present, and if it the hot afternoon, only smaller species of lizards will be observed based on Bergmann’s rule. Methods To collect data, initially the Natures Notebook mobile app was utilized. Later, it was found more convenient to keep data physically. On a printed excel sheet, observations of date, time of day, and lizard species present in the desired location were recorded. Lizard mass was not recorded, as the study was strictly observational. The location for observations was the space between (approx. two meters squared) and approximately one meter around the specific plants velvet mesquite-1 and parry’s agave-2. Accepted species of lizards found in Krutch garden are the eastern collared lizard (Crotaphytus collaris), desert spiny lizard (Sceloporus magister), sonoran spotted whiptail (Aspidoscelis sonorae), and western whiptail (Aspidoscelis tigris). However, only the S. magister and the A. sonorae were present and observed in this study. To answer the question, only the time of day and the species of lizard present were needed to measure the density of the lizard species during certain time periods throughout the day, which ranged from 7:40am to 3:40pm. These times were based on a convenience basis with no set time intervals to measure. The observed time periods were at 7:40am, 9:25am, 12:30pm, 12:45pm, 12:50pm, 1:20pm, 1:40pm, and 3:40pm, all on different days. Results During observation periods, only the species of A. sonorae and S. magister were observed. A third species, sight-identified as the ornate tree lizard, Urosaurus ornatus, was also commonly spotted. However, it was not on the species checklist provided by Natures Notebook and thus was not recorded. Of the two observed species, there were some general findings. S. magister was a larger lizard with greater body girth than the lean A. sonorae. At the earliest time 7:40AM, no lizards were present. At the later times, there was …show more content…
This leads to the question, if more lizard species were observed in Krutch gardens, would they all have a positive Bergmann’s cline, or would they have a reversed cline as in the case of S. graciosus? Pursuing a study where more species were observed, with set time intervals throughout the day and with weights recorded would be valuable as well to confirm with increased certainty or to negate whether the different lizard species do exhibit a positive Bergmann’s cline. If possible, it would also be interesting to compare lizard species from Krutch gardens to lizard species of a higher elevation, such as Mt. Lemmon, to see if the same results are
Several lizard species inhabit the University of Arizona’s Joseph Wood Krutch Gardens and interact with their environment in different ways. One such way is thermoregulation, which is influenced by body size and environmental temperature. Lizards are ectotherms, meaning they do not self-maintain internal body temperatures; instead, they are the same temperature as the surrounding environment. A rule that explains body mass and temperature correlations, called Bergmann’s rule, predicts a positive correlation between animal body mass and elevation. At higher elevations temperatures are lower, so this rule predicts that larger animals live in cooler environments (Pincheira-Donoso et al, 2008). However, Bergmann’s rule has only been shown in mammals and birds, but not necessarily for reptiles (Ashton e al, 2003). Only about 75 percent of ectotherms conform to Bergmann’s rule, however this number is under scrutiny and is believed to be lower (Pincheira-Donoso et al, 2008). In other cases, scaled reptiles known as squamates have reversed Bergmann’s clines, meaning the opposite of the rule is true because they are efficient at regulating their body temperatures by exhibiting specific behaviors (Sears 2004). Based on this interesting concept of whether ectotherms, or lizards specifically, exhibit Bergmann’s rule, a new study was formed with the following question: Do certain species of lizards prefer to occupy the space around velvet mesquite-1 (Prosopis velutina) and parry’s agave-2 (Agave parryi) during different times of the day in Krutch gardens? It is predicted if it’s a different time of day, such as morning hours versus evening hours, then there will be different lizard species visiting the area surrounding the two indicated plants. If it is a cooler temperature in the early morning or late evening, then either no lizards or only larger species of lizards will be present, and if it the hot afternoon, only smaller species of lizards will be observed based on Bergmann’s rule. Methods To collect data, initially the Natures Notebook mobile app was utilized. Later, it was found more convenient to keep data physically. On a printed excel sheet, observations of date, time of day, and lizard species present in the desired location were recorded. Lizard mass was not recorded, as the study was strictly observational. The location for observations was the space between (approx. two meters squared) and approximately one meter around the specific plants velvet mesquite-1 and parry’s agave-2. Accepted species of lizards found in Krutch garden are the eastern collared lizard (Crotaphytus collaris), desert spiny lizard (Sceloporus magister), sonoran spotted whiptail (Aspidoscelis sonorae), and western whiptail (Aspidoscelis tigris). However, only the S. magister and the A. sonorae were present and observed in this study. To answer the question, only the time of day and the species of lizard present were needed to measure the density of the lizard species during certain time periods throughout the day, which ranged from 7:40am to 3:40pm. These times were based on a convenience basis with no set time intervals to measure. The observed time periods were at 7:40am, 9:25am, 12:30pm, 12:45pm, 12:50pm, 1:20pm, 1:40pm, and 3:40pm, all on different days. Results During observation periods, only the species of A. sonorae and S. magister were observed. A third species, sight-identified as the ornate tree lizard, Urosaurus ornatus, was also commonly spotted. However, it was not on the species checklist provided by Natures Notebook and thus was not recorded. Of the two observed species, there were some general findings. S. magister was a larger lizard with greater body girth than the lean A. sonorae. At the earliest time 7:40AM, no lizards were present. At the later times, there was …show more content…
This leads to the question, if more lizard species were observed in Krutch gardens, would they all have a positive Bergmann’s cline, or would they have a reversed cline as in the case of S. graciosus? Pursuing a study where more species were observed, with set time intervals throughout the day and with weights recorded would be valuable as well to confirm with increased certainty or to negate whether the different lizard species do exhibit a positive Bergmann’s cline. If possible, it would also be interesting to compare lizard species from Krutch gardens to lizard species of a higher elevation, such as Mt. Lemmon, to see if the same results are