Color Cognition of African Lions (Panthera leo) in a Novel Learning Task
Principal Investigator: Claire Thiele, B.S., Kent State University
Mentor: Angela Ferguson, M.S., ALERT
African Lion Environmental Research Trust Internship, July 2018
Abstract
Cognition has been found to be an effective way to measure intelligence and a common technique to compare humans to other species. In this study, lion (Panthera leo) memory is focused upon due to their vulnerable conservation status. Relating lions to humans through anthropomorphic features is an initiative to venerate this species. Colors can be associated with memories, commonly seen in humans, and according to this study’s findings, also within captive lions (n=2) of the ALERT program in Victoria Falls, Zimbabwe. In a novel learning task, three primary colored buckets were placed within the lions’ enclosure. Meat was placed under the blue bucket during the first week of data collection to associate a reward with the color blue. After the first week, meat was absent until given as a reward to the successful individual. Success was defined as making contact with the blue bucket. Response time and success rate were measured. It was hypothesized: (1) The lions would learn quickly thus the response time would decrease over time, (2) Both lions would learn just as efficiently by having the same success rate and, (3) decreasing response time. Results support hypotheses 1 and 2, but could not support hypothesis 3 indicating that Panthera leo are capable of learning rapidly with variation amongst individuals.
Key Words: Cognition; color; African lion (Panthera leo)
The ability to learn can reveal an individual's probability of survival and success in life (Healy et al, 2009). Brain to body size ratio is a clear indicator of intelligence (Benson-Amram et al, 2015). The larger the brain compared to body, the higher mental capacity an individual will retain. Learning is also associated with a social lifestyle (Dunbar, 1998). Social animals are constantly interacting with conspecifics and formulating relationships based on multiple variables and circumstances. This causes an increase in neurological formation and, thus, creating a being with higher intelligence. The social brain hypothesis has been studied thoroughly in many other species (Bonabeau, et al 2000; Reader & Laland, 2002; Connor, 2007) and can attribute to lions’ (Panthera leo) high cognitive abilities.
Novel learning tasks are common mechanisms to measure cognition, usually involving a puzzle, or exercise, that requires critical thinking to be solved with a reward in return. Tasks utilizing color are also common in research to measure cognition and behavior, most involving humans (Elliot et al, 2007; Mehta & Zhu, 2009; Lichtenfeld et al, 2012). Color leaves a lasting impression on the viewer, enhancing the chance of retention (Kimura et al, 2013). This current study combines novel problem-solving and color memory to explore the intelligence of the African Lion (Panthera leo).
Although there is limited research on lion cognition it has already been found that lions adapt and learn quickly in situations involving a novel task and a food reward (Borrego and Gaines, 2016; Borrego and Dowling, 2016). Scarce prior research may be due to their conspicuous behavior and conservation status. To build up research within this species as well as awareness for their vulnerable population levels (Bauer et al., 2016) their memory was tested by observing response time to a reward through retention and recollection of a specific color. Hypotheses formed were as follows: (1) The lions would learn quickly by the response time decreasing over time, (2) Both lions would learn just as efficiently by having the same success rate, and (3) decreasing response time.
Methods
The lions, Kion and Khalanga (n=2), of the ALERT (African Lion Environmental Research Trust) Chamabonda pride in Victoria Falls, Zimbabwe were compared. Born 5th June 2017, Kion and Khalanga were 13 months old during the study--26/06/18-13/07/18. Only two of the four lions were used due to habitat constraints as well as the fact that one individual had inadequate eyesight. To understand their cognitive abilities, a task to remember a particular color was given to them.
Kion and Khalanga were restricted to their caged partition on the far, left end of the enclosure before data collection. Three different colored buckets--red, blue, and yellow--were placed at equidistant yet distinct points within their enclosure (Figure 1). The buckets were only seen by the lions during data collection and hidden all other times to avoid interactions outside of trials. Arrangement of the buckets was changed every trial to maintain stochasticity. Prior to data collection, the blue bucket was designated to have a reward associated with it, becoming the “successful” choice for the lions. Blue, with the lowest wavelength of the primary colors, has the lowest chance of attracting the lions, ensuring the intent of the lions being purely based on memory. Meat was put under this blue bucket out of the lions’ view. As the lions are fed every other day, trials were done on non-feeding days to ensure the lions would participate.
Data was collected within the enclosure for best viewing of individuals. Video recordings of trials were utilized for most accurate results. A stop watch was also used to record data live. Data observations commenced once the gate to the partition was opened. Lions would immediately rush out and investigate the novel items. The first bucket they touched was considered their “choice”. Success was defined as an individual making contact with the blue bucket. Each lion would approach a bucket and investigate the same one for the remainder of the trial. Additionally, the presence of one lion would deter the conspecific from approaching that occupied bucket. Thus, each lion only chose one bucket and only one lion was successful for each trial.
During the first week (three trials) the blue bucket had meat underneath it to associate a reward with the color blue. All future trials had no meat underneath the buckets, however, every other day, the successful lion was rewarded with meat afterwards to further enforce this behavior. After retrieving the buckets from the lions, meat was placed inside the blue bucket and given to the correct lion so they knew what they were being rewarded for. Buckets were removed from the enclosure immediately after an individual was successful to avoid the lions from eating and/or destroying them. Response time to the blue bucket was documented for all trials as well as which lion was successful.
Figure 1. Schematic of lions’ enclosure with a caged partition and three primary colored buckets.
Results
Three comparisons were made within this study: (1) Trial and response time, (2) Lion and success, and (3) Lion and response time.
Trial and response time:
To see how quickly they could learn, trial and the lions' response time to the blue bucket were compared (Figure 2). It was hypothesized that response time would decrease over time as they learned progressively faster. A linear regression was used to test this hypothesis (p-value=0.048; R2=0.28).
Lion and success:
Kion and Khalanga’s success rate was compared with the expectation that there would be no significant difference. Results were best depicted using a binomial distribution as well as a z-test. Binomial distributions, or success rates, for Kion and Khalanga were as follows: 0.5 and 0.75. To test the difference between these two values a z-test was utilized to find no statistical significance (Figure 3, p-value=0.318)
Lion and response time:
Kion and Khalanga's response times to the blue bucket were also compared to identify individualistic learning abilities. It was expected that the response times of the lions would decrease at the same rate, yet a t-test portrayed a statistical significance between the lions (Figure 4, p-value=0.027).
Figure 2. Average of both lions’ response times (s) to the blue bucket over all trials (n=9) (p=0.048).
Figure 3. Each lion’s success rate across all trials (n=9) (p=0.318). Success was defined as contacting the blue bucket.
Figure 4. Each lion’s response times to the blue bucket (p=0.027). If a lion did not make contact with a bucket the data point was omitted. This happened to Kion once and Khalanga four times. The first trial, control, was also omitted to reduce outliers and compare each lion’s learning abilities.
Discussion
Results supported hypotheses (1) The lions would learn quickly and thus response time will decrease throughout trials and (2) Both lions would learn just as efficiently by having the same success rate (Figure 3). Hypothesis 3--both lions would learn equally efficiently with a decreasing response time--could not be supported (Figure 4).
Response time decreased significantly over time from the first day of the novel learning task revealing the extremely rapid memory formation within lions (Figure 2, p-value=0.048). From trial 1 to 2 there is a massive decline in response time, indicating that learning begins on the first day. A regression excluding the first trial yields a non-significant difference (p-value=0.12) implying that once the task was learned this process was not improved throughout all trials; only improved upon when in relation to the first time the task was presented.
Although Kion and Khalanga had no significant difference between success rate (Figure 3, p-value=0.318), supporting the second hypothesis, they did have different response times (Figure 4, p=0.027), rejecting the third hypothesis. This suggests individualistic variation in learning abilities. but would need to be examined further to distinguish definitively. Interestingly, once a lion had chosen a bucket their presence deterred the other from approaching that location. This may have influenced the effects on success rate and response time. If each lion were tested individually this could have been avoided.
Color cognition all depends on how an individual perceives color. Lions’ vision has been proven to be trichromatic, as they have both rods and cones, but the actual tones or pigments they see may be quite different to how humans experience the primary colors (Spector, 2018). This is mainly due to the abundance of rods versus cones, the cell detecting light rather than color (Peel 2011). Despite the lack of vibrancy in feline color vision, Kion and Khalanga were still successful in identifying and retaining the color blue. According to prior research, lions have been known to detect blues and greens more readily than red (Peel 2011; Spector 2018). This may be the reason for the lions’ success rates. To mitigate this problem, blues and greens should be omitted from color memory tasks to ensure the feline’s approach to the object is based solely on memory and not visual attraction. In addition, utilizing multiple hues of the same color could help us determine how well lions perceive color.
Lions also have a great sense of smell due to the presence of the Jacobson’s organ on the roof of their mouth (ALERT 2019). Since this is the case, it is possible that the lions chose the blue bucket based on the lingering scent of meat. The bucket was rinsed out only when excessive liquid from the meat remained. For future studies, careful cleaning of the bucket should be enforced to ensure the intent of the lions is entirely based on memory and not scent from past rewards.
To further explore lion cognition, I would like to continue this study by using different objects with the same primary colors to see if they persist to visit the blue object out of attraction or if they really are retaining information. This could further prove the impressive memory capabilities lions possess. I would also like to replicate this study with the lions of my home zoo; Cleveland Metroparks Zoo of Cleveland, OH, USA. If this can be proven within multiple individuals of different origins it will provide more insight upon this fascinating species.
This study has continued to show that lions learn quickly and associate colors with memories. It has only begun to scratch the surface of how well these animals form memories and apply them to everyday life. This high cognition could be utilized in conservation efforts. For instance, if an animal could learn and remember that a particular color is good or bad it could either attract or deter the animal from visiting that area. This could limit wildlife poaching and other human-wildlife conflicts.
Humans also utilize memories and learning to handle issues. I firmly believe if lions are continuously compared to humans so that the public can see how similar we are it will improve the appreciation and fascination for this species. In turn, this could decrease the trophy poaching of lions and increase their population levels in the wild. In captivity, lions may be granted more funding for better enclosures, enrichment, and conservation education. Furthering pioneer studies such as this one, comparing a threatened species to humans, may bring rise to their deteriorating population levels.
Acknowledgements
Where to even begin… I first would like to thank my father. For being number one on my support team throughout my career, especially during my first trip to Africa. Angela Fergusonleadership and advice on career goals. Your hospitality meant so much and I appreciate every day I got to spend with you in the field. Lenard Ngwenya, lion mastercherish
Other lion tamerstheir assistance in data collection. Spencer Bergeron Other volunteers and internsnce Taylor for helping me make my first purchase in Zimbabwe—the buckets
All my other friends of ALERT!
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