Sexual Dimorphism In Arctic Foxes
Carleton University
Laboratory Report
Course #: BIOL1004A Lab #: 2
Sexual Dimorphism in Arctic Foxes
Kathryn Brechun
Date Performed: January 29, 2014
Date Submitted: February 12, 2014
Lab Period: Thursday AM
Station: B3
T.A: Genevieve Perkins
Abstract
Sexual dimorphism in the feeding structures and sexual selection is a common phenomenon in nature. The purpose of this lab was to determine if canine size and bite force is sexually dimorphic in Arctic foxes (Vulpes lagopus). The canine width of female and male fox skulls was measured, as well photographs of fox skulls were used to measure bite force. Data from the class was used to show evidence of arctic fox males to be found to have larger canine width as well as a larger …show more content…
bite force than females. The class data collected was analyzed using a t-test and also a p-value. The t-test was used to compare average canine width and average bite force in Arctic foxes between male and females to determine sexual dimorphism. For both average canine width and bite force, the p value was less than 0.05, giving evidence that bite force and canine width in male and female foxes are significant. The data suggested that the differences in the feeding structures of the Arctic fox have resulted from sexual selection, food competition between males and females and dimorphic niche hypothesis. These three hypotheses explain the effects bite force and canine width exhibit sexual dimorphism in male and female Arctic foxes.
Introduction
Sexual dimorphism is a largely known phenomenon and is large focus on evolutionary studies due to, Charles Darwin theory of natural selection in the book “Origin of Life” that was published in 1860.
It is the systematic physical differences between individuals of different sex in the same species. Males and Females in most animals have different reproductive organs, and other sexual differences in traits such as their size, colour, odour and shape. Sexual dimorphism is common in very common in nature. The collared lizard and the purple-throated Carib are common sexual dimorphism. The collared lizard (Crotaphytus collaris) is known its enlarged jaws and jaw adductor muscles of male and the female has smaller much smaller jaw and jaw adductor. The distinction between the jaw strength and size is an example of sexual dimorphism as well as intersexual selection as males with larger mouths attract the females. This creates interest in the species to determine the evolution of the collared lizard as sexual dimorphism allows scientist to have the ability to enhance reproductive success and survival. This sexual dimorphism also occurs in many other species such as the purple-throated carib ( Eulampis jugalaris). This is a type of hummingbird that is characterized by the male size, and the beak sizes of the female and male(Gowda,2012). The female’s beak is 20% longer and 30% more curved than the males(Gowda, 2012).Dimorphism is common in feeding structures as they can be important …show more content…
for the fitness of animals. In Walker and Rypstra’s study of sexual dimorphism in wolf spiders, the females are much larger and consume more prey than the males, which suggests that the feeding behavior between the sexes are different. This suggests that the feeding behaviors tell us that females have been selected to maximize their energy intake by attacking more prey and in some cases larger pre. The females also have larger venom glands than males, which suggest that there is advantage in the sexes. As a result it was seen in the study that female spiders require more energy for their reproductive roles to influence sexual dimorphism in feeding behavior.
The Sexual dimorphism is present in the Arctic fox (Vulpes lagopus). The Arctic fox lives in the Arctic regions of the Northern Hemisphere in the cold environments. Arctic fox prey includes lemmings, fish, birds and other marine life. The arctic fox has shorter legs neck and smaller ears, is means that there is a smaller surface area to lose heat enabling the fox to be in such harsh cold conditions.
The size of an arctic fox male is slightly larger than the female, and there are differences in the feeding patterns of the male and female fox. The possible reasons for the sexual dimorphism in the arctic fox are their feeding structure, population of prey available, food availability and the geographical variation of their location.
The purpose of this lab was to determine if canine size and bite force is sexually dimorphic in Arctic foxes. Feeding structures exists in other mammals that result in sexual dimorphism. We are interested in determining the feeding structures in the arctic fox effect the sexual dimorphism of the male and female fox. Thus, sexual dimorphism in feeding structures exists in other mammals. We were thus interested to determine if it was also the case in Arctic foxes. Examples of feeding structures in sexual dimorphism are black bears (Ursus americanus). There is sexual dimorphism in the bear sizes, as the sizes of male black bears are nearly twice as heavy as the heaviest female black bears (Miller et al., 2009). The male bears size and weight serves as an advantage for the male bears when in combat (Miller et al., 2009).
In the Saber cat (Smilodon fatalis) the mouth also plays an important role in reproductive behavior. In Christiansen and Harris’s study of the Pantherines and Saber cat, are similar in the jaw strength to kill their prey and an impact on survival, growth and reproduction in females (Christiansen and Harris, 2012). Males have larger body sizes, strong upper canines and stringer bite forces allowing for larger prey to be killed than females. Therefore the stronger bite forces in male Pantherines and Saber cats can be a selective advantage as well as sexual combat to compete for the better female (Christiansen and Harris, 2012). Thus the males feed on larger prey and females consume smaller prey maximizing energy for reproduction (Christiansen and Harris, 2012)
Therefore, feeding structures exist in other mammals resulting in interest to learn more about whether sexual dimorphism in feeding structures exist in Arctic foxes.
Methods
The measurement of canine size: In the first part of the lab, I measured the length of the arctic skull fox. Using a ruler I measured the length of the skull from the posterior to the anterior edges of the skull in the 10 sets of photographs given. The skull length (SL) was measured using a 30 cm ruler and was recorded in cm. I measured the temporal muscle (AOT) by using a piece of tracing paper over the photograph of the Arctic fox skull and using a pencil, tracing an outline of the origin of the temporalis muscle (AOT) on the skull. The trace paper was than placed on top of a 1cm by 1 cm grid paper to determine the area of origin of the temporalis muscle in cm2 by counting the number of squares (an estimate was used for partial squares). The relative area was than calculated using the temporalis muscle and skull length measurements. See Figure 5 of Lab2- Sexual dimorphism in Arctic foxes in the ‘Introduction to Biology 1004 Laboratory Manual Winter Term 2015 workbook. The results for the temporalis muscle and skull length were recorded in a chart including the skill ID number of each skull.
Measurement of bite force:
In part two of the lab, I measured ten actual arctic fox skulls five female and five male. I used a Vernier Caliper to measure the distances in millimeters by looking at the zero position on the vernier scale to immediate left of the zero mark on the vernier scale. I measured the distance in centimeters (cm) between the tip of the angular process and the tip of the mandibular condyle using a vernier caliper in millimeters (mm). The length measured is the in-lever arm (LILA). Next, I measured the distance between the tip of the mandibular condyle and the base of the anterior edge of the canine (as indicated in Figure 6 Lab2- Sexual dimorphism in Arctic foxes in the ‘Introduction to Biology 1004 Laboratory Manual Winter Term 2015) using a Vanier calliper in millimetres. This measurement is the length of the out-lever arm (LOLA). The measurements above were recorded and converted to centimetres (cm). The mechanical advantage was than recorded by dividing the out-lever arm by the in-lever arm. Fiver males and five females were recorded as well as the skull id.
Statistical analysis:
A t-test was used to determine sexual dimorphism in Artic fox canine width and sexual dimorphism in Arctic fox bite force. When interpreting the results from the t-test, the p value is observed. When p0.05, thee results are not statistically significant. Microsoft Excel was used to find the t-test.
Results
In the lab, the bite force and canine width of Arctic fox skulls were measured for five female and five male skulls as well as 10 photographed skull images of arctic fox’s. The bite force of male and female Artic foxes, a t-test was used to determine if the sex of the fox has influenced the bite force of the artic fox. The bite force mean in the t-test for the Arctic fox skulls resulted in a low p-value of less than 0.5. The results prove that the sex has an influence on the bite force in the Artic fox.
Average bite force in females was 1.77N(± 0.23N) compared to 1.91N(± 0.18N) in males (figure 1). This difference was statistically significant (t-test: T=1.52, p=0.042). The p value is less than 0.05 thus, signifies that difference in mean bite force in males and females is significant and has is sexually dimorphic in the Arctic fox.
Figure 1. Average bite force of female and male Arctic foxes (Vulpes lagopus), with standard deviation bars.
A t-test was also used to determine if the sex of an Arctic fox influences canine width. The result from the t-test showed the probability in the difference of male and female canine width is due to the change in the width is very low. Therefore sex does influence canine width in female and male Arctic foxes. Average canine width in males was 8.10mm (+/- 0.84mm) compared to 7.43mm (+/- 1.10mm) in females (figure 2). This difference was statistically significant (t-test: T = 2.63, p = 0.0111). The p value is less than 0.05 which signifies that difference in mean canine width in males and females is significant, and therefore canine width is sexually dimorphic in the Arctic fox.
Figure 2. Average canine width of female and male Arctic foxes (Vulpes lagopus), with standard deviation bars.
Discussion
The purpose of this lab was to compare average canine width and average bite force between male and female Arctic foxes (Vulpes lagopus) to determine if they are sexually dimorphic. The results from the experiment showed that there is a statistically significant difference in female and male bite force as well as canine width. Males were found to have a larger bite force and canine width than that of females.
The evolutionary cause of sexual dimorphism in the Artic fox can be explained through two of the three hypotheses that were discussed in the analytical session were sexual selection and food competition between males and females.
The hypothesis of sexual selection is derived from Darwin’s observations and results in his book ‘On the Origin of Species”. Darwin’s sexual selection hypothesis suggests that sexual dimorphism has evolved in characters that extend to an advantage in competition for males and females to mate together or mate choice that are selected in a sex. (Hedrick and Temeles, 1989). The bite force and canine width in the male Arctic fox can be stronger for fighting abilities and the ability to capture prey for food. In Lappin and Husak’s study of weapon performance in the Collard Lizard (Crotaphytus collaris), the male lizard has a larger head than females and this male-biased head dimorphism help with combat situations. The head size of a male lizard may also be related to territory and mating success. Sexual selection reacts on traits related to the fitness; in result the bite force and canine width are characteristics that can increase the mating success of females and males. An important component of fitness in nature is dominance, and this may be the reason that sexual dimorphism evolved in the Arctic fox through female mating preferences for males with larger bite force and canine width.
The hypothesis of food competition between males and females can explain why bite force and canine width are sexually dimorphic in the Arctic fox Food competition between the sexes relates to Artic fox because the differences in bite force and canine width is a result of males is chosen to maximize their energy intake by attacking more prey or perhaps larger prey. In the Walker and Rypstra’s study, the examination of feeding behavior in wolf spiders (Licosidae) demonstrates that females have been selected to increase their energy intake to a maxima by attacking more prey, and sometimes attacking larger prey than males. Females also as said earlier contained larger venom glands than males, as a result giving them an additional advantage when killing prey and consuming prey, consequently improving their feeding ability towards the food competition between males and females. Therefore reasons for sexual dimorphism in the Arctic fox may be the result of different feeding structures, food availability and prey density. The two hypothesis discussed can explain why the bite force and canine width are sexually dimorphic in the Arctic fox although sexual selection and food competition between sexes are more likely to have been the cause of sexual dimorphism in this species.
There are many different experiments that could be run in order to test how sexual selection can help explain the sexual dimorphism observed in the Artic fox. An experiment could be one involving correlation analysis where the relationship between bite force and fitness is examined in an environment of males and females of different sizes and quantity. Therefore you could compare the bite force of a male Arctic fox with the number of offspring produced by the male. The result may help to determine whether the bite force helps improve the fitness of arctic fox’s.
In Lappin and Husak’s scientific study of weapon performance in the Collard Lizard (Crotaphytus collaris), they evaluated the power of bite force in predicting area and estimates of fitness, and three correlation analyses were performed.
The bite force in the collared lizard was compared to territory size, the mating success, number of females inseminated and the reproductive output in the male lizard. As shown in the experiment, the individual with the greatest bite force performance maintained the largest territory, resulting in an overlap of most of the females, and had resulted in the second highest potential reproductive output. In contrast, lowest bite force individuals had the smallest territory, which overlapped the a smaller amount of females, has accounted for the lowest estimated number of inseminated females, and had the lowest potential reproductive output (Lappin and Husak, 2005). Food competition between males and females can also help explain sexual dimorphism in the Arctic
fox.
To test this hypothesis, an equal number of males and females could be observed in an environment with a certain number of one types of prey, varying in size. The carry out of the experiment, can result in the help of food competition to prove whether larger canine width and stronger bite force in the male Arctic fox enables males to capture more prey than female or if smaller canine width and weaker bite force in Arctic fox males. The sexual variation in the size of the prey can be differed resulting in the observation whether or not larger canine width and stronger bite force in males allows the capability to capture larger prey than females. In Walker and Rypstra’s study of sexual dimorphism in wolf spiders, females were generally larger than males and consumed more prey, suggesting that feeding behavior between the sexes were different (Walker and Rypstra, 2001).
In conclusion, the sexual dimorphism in arctic foxes from the experiment showed that there is a statistically significant difference in female and male bite force as well as canine width. Males were found to have a larger bite force and canine width than that of females. This concludes that the relative area of the temporalis (RAOT) in arctic foxes has a food connection allowing males to capture more prey than female’s increases their energy consumption. The mechanical advantage tells us that the canine width also gives a sexual and food advantage due to the size of the arctic fox. The results inform the scientific community by communicating that sexual dimorphisms enables positive and negatives for Arctic foxes and gives us the chance to understand more about sexual dimorphism and the different ways animals are caused by it. Whether that is my canine width, bite force, food connection between sexes, sexual selection. This allows us to compare and contrast between the many species similar to the ones written about.
References
Christiansen, P., Harris, J., & Farke, A. (2012). Variation in Craniomandibular Morphology and Sexual Dimorphism in Pantherines and the Sabercat Smilodon fatalis. PLoS ONE, E48352-E48352.
Gowda, V., Temeles, E. J., and W. J. Kress. 2012. Territory fidelity to nectar sources by Purple-throated Caribs, Eulampis jugularis. The Wilson Journal of Ornithology 124:81-86.
Hedrick, Ann V., and Ethan J. Temeles. "The Evolution of Sexual Dimorphism in Animals: Hypotheses and Tests." Trends in Ecology & Evolution (1989): 136-38.
Lappin, A., & Husak, J. (2005). Weapon Performance, Not Size, Determines Mating Success and Potential Reproductive Output in the Collared Lizard (). The American Naturalist, 426-436.
Miller, E., Mahoney, S., Kennedy, M., & Kennedy, P. (2009). Variation, Sexual Dimorphism, and Allometry in Molar Size of the Black Bear. Journal of Mammalogy, 491-503.
Persons, M., Walker, S., Rypstra, A., & Marshall, S. (2001). Wolf spider predator avoidance tactics and survival in the presence of diet-associated predator cues (Araneae: Lycosidae). Animal Behaviour, 43-51.
Laboratory Report
Course #: BIOL1004A Lab #: 2
Sexual Dimorphism in Arctic Foxes
Kathryn Brechun
Date Performed: January 29, 2014
Date Submitted: February 12, 2014
Lab Period: Thursday AM
Station: B3
T.A: Genevieve Perkins
Abstract
Sexual dimorphism in the feeding structures and sexual selection is a common phenomenon in nature. The purpose of this lab was to determine if canine size and bite force is sexually dimorphic in Arctic foxes (Vulpes lagopus). The canine width of female and male fox skulls was measured, as well photographs of fox skulls were used to measure bite force. Data from the class was used to show evidence of arctic fox males to be found to have larger canine width as well as a larger …show more content…
bite force than females. The class data collected was analyzed using a t-test and also a p-value. The t-test was used to compare average canine width and average bite force in Arctic foxes between male and females to determine sexual dimorphism. For both average canine width and bite force, the p value was less than 0.05, giving evidence that bite force and canine width in male and female foxes are significant. The data suggested that the differences in the feeding structures of the Arctic fox have resulted from sexual selection, food competition between males and females and dimorphic niche hypothesis. These three hypotheses explain the effects bite force and canine width exhibit sexual dimorphism in male and female Arctic foxes.
Introduction
Sexual dimorphism is a largely known phenomenon and is large focus on evolutionary studies due to, Charles Darwin theory of natural selection in the book “Origin of Life” that was published in 1860.
It is the systematic physical differences between individuals of different sex in the same species. Males and Females in most animals have different reproductive organs, and other sexual differences in traits such as their size, colour, odour and shape. Sexual dimorphism is common in very common in nature. The collared lizard and the purple-throated Carib are common sexual dimorphism. The collared lizard (Crotaphytus collaris) is known its enlarged jaws and jaw adductor muscles of male and the female has smaller much smaller jaw and jaw adductor. The distinction between the jaw strength and size is an example of sexual dimorphism as well as intersexual selection as males with larger mouths attract the females. This creates interest in the species to determine the evolution of the collared lizard as sexual dimorphism allows scientist to have the ability to enhance reproductive success and survival. This sexual dimorphism also occurs in many other species such as the purple-throated carib ( Eulampis jugalaris). This is a type of hummingbird that is characterized by the male size, and the beak sizes of the female and male(Gowda,2012). The female’s beak is 20% longer and 30% more curved than the males(Gowda, 2012).Dimorphism is common in feeding structures as they can be important …show more content…
for the fitness of animals. In Walker and Rypstra’s study of sexual dimorphism in wolf spiders, the females are much larger and consume more prey than the males, which suggests that the feeding behavior between the sexes are different. This suggests that the feeding behaviors tell us that females have been selected to maximize their energy intake by attacking more prey and in some cases larger pre. The females also have larger venom glands than males, which suggest that there is advantage in the sexes. As a result it was seen in the study that female spiders require more energy for their reproductive roles to influence sexual dimorphism in feeding behavior.
The Sexual dimorphism is present in the Arctic fox (Vulpes lagopus). The Arctic fox lives in the Arctic regions of the Northern Hemisphere in the cold environments. Arctic fox prey includes lemmings, fish, birds and other marine life. The arctic fox has shorter legs neck and smaller ears, is means that there is a smaller surface area to lose heat enabling the fox to be in such harsh cold conditions.
The size of an arctic fox male is slightly larger than the female, and there are differences in the feeding patterns of the male and female fox. The possible reasons for the sexual dimorphism in the arctic fox are their feeding structure, population of prey available, food availability and the geographical variation of their location.
The purpose of this lab was to determine if canine size and bite force is sexually dimorphic in Arctic foxes. Feeding structures exists in other mammals that result in sexual dimorphism. We are interested in determining the feeding structures in the arctic fox effect the sexual dimorphism of the male and female fox. Thus, sexual dimorphism in feeding structures exists in other mammals. We were thus interested to determine if it was also the case in Arctic foxes. Examples of feeding structures in sexual dimorphism are black bears (Ursus americanus). There is sexual dimorphism in the bear sizes, as the sizes of male black bears are nearly twice as heavy as the heaviest female black bears (Miller et al., 2009). The male bears size and weight serves as an advantage for the male bears when in combat (Miller et al., 2009).
In the Saber cat (Smilodon fatalis) the mouth also plays an important role in reproductive behavior. In Christiansen and Harris’s study of the Pantherines and Saber cat, are similar in the jaw strength to kill their prey and an impact on survival, growth and reproduction in females (Christiansen and Harris, 2012). Males have larger body sizes, strong upper canines and stringer bite forces allowing for larger prey to be killed than females. Therefore the stronger bite forces in male Pantherines and Saber cats can be a selective advantage as well as sexual combat to compete for the better female (Christiansen and Harris, 2012). Thus the males feed on larger prey and females consume smaller prey maximizing energy for reproduction (Christiansen and Harris, 2012)
Therefore, feeding structures exist in other mammals resulting in interest to learn more about whether sexual dimorphism in feeding structures exist in Arctic foxes.
Methods
The measurement of canine size: In the first part of the lab, I measured the length of the arctic skull fox. Using a ruler I measured the length of the skull from the posterior to the anterior edges of the skull in the 10 sets of photographs given. The skull length (SL) was measured using a 30 cm ruler and was recorded in cm. I measured the temporal muscle (AOT) by using a piece of tracing paper over the photograph of the Arctic fox skull and using a pencil, tracing an outline of the origin of the temporalis muscle (AOT) on the skull. The trace paper was than placed on top of a 1cm by 1 cm grid paper to determine the area of origin of the temporalis muscle in cm2 by counting the number of squares (an estimate was used for partial squares). The relative area was than calculated using the temporalis muscle and skull length measurements. See Figure 5 of Lab2- Sexual dimorphism in Arctic foxes in the ‘Introduction to Biology 1004 Laboratory Manual Winter Term 2015 workbook. The results for the temporalis muscle and skull length were recorded in a chart including the skill ID number of each skull.
Measurement of bite force:
In part two of the lab, I measured ten actual arctic fox skulls five female and five male. I used a Vernier Caliper to measure the distances in millimeters by looking at the zero position on the vernier scale to immediate left of the zero mark on the vernier scale. I measured the distance in centimeters (cm) between the tip of the angular process and the tip of the mandibular condyle using a vernier caliper in millimeters (mm). The length measured is the in-lever arm (LILA). Next, I measured the distance between the tip of the mandibular condyle and the base of the anterior edge of the canine (as indicated in Figure 6 Lab2- Sexual dimorphism in Arctic foxes in the ‘Introduction to Biology 1004 Laboratory Manual Winter Term 2015) using a Vanier calliper in millimetres. This measurement is the length of the out-lever arm (LOLA). The measurements above were recorded and converted to centimetres (cm). The mechanical advantage was than recorded by dividing the out-lever arm by the in-lever arm. Fiver males and five females were recorded as well as the skull id.
Statistical analysis:
A t-test was used to determine sexual dimorphism in Artic fox canine width and sexual dimorphism in Arctic fox bite force. When interpreting the results from the t-test, the p value is observed. When p0.05, thee results are not statistically significant. Microsoft Excel was used to find the t-test.
Results
In the lab, the bite force and canine width of Arctic fox skulls were measured for five female and five male skulls as well as 10 photographed skull images of arctic fox’s. The bite force of male and female Artic foxes, a t-test was used to determine if the sex of the fox has influenced the bite force of the artic fox. The bite force mean in the t-test for the Arctic fox skulls resulted in a low p-value of less than 0.5. The results prove that the sex has an influence on the bite force in the Artic fox.
Average bite force in females was 1.77N(± 0.23N) compared to 1.91N(± 0.18N) in males (figure 1). This difference was statistically significant (t-test: T=1.52, p=0.042). The p value is less than 0.05 thus, signifies that difference in mean bite force in males and females is significant and has is sexually dimorphic in the Arctic fox.
Figure 1. Average bite force of female and male Arctic foxes (Vulpes lagopus), with standard deviation bars.
A t-test was also used to determine if the sex of an Arctic fox influences canine width. The result from the t-test showed the probability in the difference of male and female canine width is due to the change in the width is very low. Therefore sex does influence canine width in female and male Arctic foxes. Average canine width in males was 8.10mm (+/- 0.84mm) compared to 7.43mm (+/- 1.10mm) in females (figure 2). This difference was statistically significant (t-test: T = 2.63, p = 0.0111). The p value is less than 0.05 which signifies that difference in mean canine width in males and females is significant, and therefore canine width is sexually dimorphic in the Arctic fox.
Figure 2. Average canine width of female and male Arctic foxes (Vulpes lagopus), with standard deviation bars.
Discussion
The purpose of this lab was to compare average canine width and average bite force between male and female Arctic foxes (Vulpes lagopus) to determine if they are sexually dimorphic. The results from the experiment showed that there is a statistically significant difference in female and male bite force as well as canine width. Males were found to have a larger bite force and canine width than that of females.
The evolutionary cause of sexual dimorphism in the Artic fox can be explained through two of the three hypotheses that were discussed in the analytical session were sexual selection and food competition between males and females.
The hypothesis of sexual selection is derived from Darwin’s observations and results in his book ‘On the Origin of Species”. Darwin’s sexual selection hypothesis suggests that sexual dimorphism has evolved in characters that extend to an advantage in competition for males and females to mate together or mate choice that are selected in a sex. (Hedrick and Temeles, 1989). The bite force and canine width in the male Arctic fox can be stronger for fighting abilities and the ability to capture prey for food. In Lappin and Husak’s study of weapon performance in the Collard Lizard (Crotaphytus collaris), the male lizard has a larger head than females and this male-biased head dimorphism help with combat situations. The head size of a male lizard may also be related to territory and mating success. Sexual selection reacts on traits related to the fitness; in result the bite force and canine width are characteristics that can increase the mating success of females and males. An important component of fitness in nature is dominance, and this may be the reason that sexual dimorphism evolved in the Arctic fox through female mating preferences for males with larger bite force and canine width.
The hypothesis of food competition between males and females can explain why bite force and canine width are sexually dimorphic in the Arctic fox Food competition between the sexes relates to Artic fox because the differences in bite force and canine width is a result of males is chosen to maximize their energy intake by attacking more prey or perhaps larger prey. In the Walker and Rypstra’s study, the examination of feeding behavior in wolf spiders (Licosidae) demonstrates that females have been selected to increase their energy intake to a maxima by attacking more prey, and sometimes attacking larger prey than males. Females also as said earlier contained larger venom glands than males, as a result giving them an additional advantage when killing prey and consuming prey, consequently improving their feeding ability towards the food competition between males and females. Therefore reasons for sexual dimorphism in the Arctic fox may be the result of different feeding structures, food availability and prey density. The two hypothesis discussed can explain why the bite force and canine width are sexually dimorphic in the Arctic fox although sexual selection and food competition between sexes are more likely to have been the cause of sexual dimorphism in this species.
There are many different experiments that could be run in order to test how sexual selection can help explain the sexual dimorphism observed in the Artic fox. An experiment could be one involving correlation analysis where the relationship between bite force and fitness is examined in an environment of males and females of different sizes and quantity. Therefore you could compare the bite force of a male Arctic fox with the number of offspring produced by the male. The result may help to determine whether the bite force helps improve the fitness of arctic fox’s.
In Lappin and Husak’s scientific study of weapon performance in the Collard Lizard (Crotaphytus collaris), they evaluated the power of bite force in predicting area and estimates of fitness, and three correlation analyses were performed.
The bite force in the collared lizard was compared to territory size, the mating success, number of females inseminated and the reproductive output in the male lizard. As shown in the experiment, the individual with the greatest bite force performance maintained the largest territory, resulting in an overlap of most of the females, and had resulted in the second highest potential reproductive output. In contrast, lowest bite force individuals had the smallest territory, which overlapped the a smaller amount of females, has accounted for the lowest estimated number of inseminated females, and had the lowest potential reproductive output (Lappin and Husak, 2005). Food competition between males and females can also help explain sexual dimorphism in the Arctic
fox.
To test this hypothesis, an equal number of males and females could be observed in an environment with a certain number of one types of prey, varying in size. The carry out of the experiment, can result in the help of food competition to prove whether larger canine width and stronger bite force in the male Arctic fox enables males to capture more prey than female or if smaller canine width and weaker bite force in Arctic fox males. The sexual variation in the size of the prey can be differed resulting in the observation whether or not larger canine width and stronger bite force in males allows the capability to capture larger prey than females. In Walker and Rypstra’s study of sexual dimorphism in wolf spiders, females were generally larger than males and consumed more prey, suggesting that feeding behavior between the sexes were different (Walker and Rypstra, 2001).
In conclusion, the sexual dimorphism in arctic foxes from the experiment showed that there is a statistically significant difference in female and male bite force as well as canine width. Males were found to have a larger bite force and canine width than that of females. This concludes that the relative area of the temporalis (RAOT) in arctic foxes has a food connection allowing males to capture more prey than female’s increases their energy consumption. The mechanical advantage tells us that the canine width also gives a sexual and food advantage due to the size of the arctic fox. The results inform the scientific community by communicating that sexual dimorphisms enables positive and negatives for Arctic foxes and gives us the chance to understand more about sexual dimorphism and the different ways animals are caused by it. Whether that is my canine width, bite force, food connection between sexes, sexual selection. This allows us to compare and contrast between the many species similar to the ones written about.
References
Christiansen, P., Harris, J., & Farke, A. (2012). Variation in Craniomandibular Morphology and Sexual Dimorphism in Pantherines and the Sabercat Smilodon fatalis. PLoS ONE, E48352-E48352.
Gowda, V., Temeles, E. J., and W. J. Kress. 2012. Territory fidelity to nectar sources by Purple-throated Caribs, Eulampis jugularis. The Wilson Journal of Ornithology 124:81-86.
Hedrick, Ann V., and Ethan J. Temeles. "The Evolution of Sexual Dimorphism in Animals: Hypotheses and Tests." Trends in Ecology & Evolution (1989): 136-38.
Lappin, A., & Husak, J. (2005). Weapon Performance, Not Size, Determines Mating Success and Potential Reproductive Output in the Collared Lizard (). The American Naturalist, 426-436.
Miller, E., Mahoney, S., Kennedy, M., & Kennedy, P. (2009). Variation, Sexual Dimorphism, and Allometry in Molar Size of the Black Bear. Journal of Mammalogy, 491-503.
Persons, M., Walker, S., Rypstra, A., & Marshall, S. (2001). Wolf spider predator avoidance tactics and survival in the presence of diet-associated predator cues (Araneae: Lycosidae). Animal Behaviour, 43-51.