Foraging

Foraging in Animals

Foraging is the process by which all living things obtain food as a source of energy, either directly through eating, storing for later consumption, or providing to other living things in the form of provision, such as a mother to her young. Animals’ ability to affect the dispersal of seeds and the pollination of plant feeds depends on their ability to forage, which is essential for the reproduction, growth, and survival of the organism through avoidance of predators. Foraging in animals plays a crucial role in determining the reproduction, growth process, and the survival of the organism through avoidance of the predators and also contributes in the animal’s ability to influence the dispersion of seeds and pollination of plant foods.

Factors Affecting Foraging Behavior

A study by Stephens, Brown and Ydenberg (2007) revealed that a foraging process requires interaction and total engagement of the predator and the dynamics of an intricate hunting environment. By considering the physical factors and the time dynamics of foraging in an environment where food distribution is patchy in nature, the successful predator must out-way the underlying constraints and properly determine important factors like: time needed to move from one food patch to the other, hunting time for the prey (food) within a food patch, the amount of energy spent in the process. Moreover, the social and environmental dynamics affects the foraging pattern and results in the organisms to acquire an adaptive behavior in the face of the varying external and internal environments.

River Otters and Foraging

River otters (Lontra Canadensis) are predators adapted to hunting in rivers while feeding on aquatic and semi-aquatic organisms given by their streamlined bodies, shorter legs with thick webbed toes, and long tails. Other important characteristic of these mammals are that they have short thick fur and the male measures approximately 4 feet tall, from head to the tip of the tail, with a mean weight of 20 to 28 pounds. However, the female river otters adults are relatively smaller in size than their male counterparts. In terms of daily energy intake, an adult otter can consume of between 1-1.5 kg of food daily: fishes, reptiles and amphibians, insects and other small organisms.

Gender Differences in River Otter Foraging

Previous observational studies have found that there exists a considerable behavioral difference in terms of environmental space utilization, social interactions and the foraging behaviors between the male and the female river otters. In contrast, female otters use their surrounding as defecation point more whereas the males use fewer sites and yet deposit more (Rostain et. al. 2012). The same study found that: in terms of social interactions, the male otters are more often social while as the females are often solitary. Stephens et al., (2007) posited that male competition for mating opportunities is more likely to be the main reason for the more social behavior among the male otters.

Influence of Weather and Other Factors on Otter Foraging

Seasonal and geographical weather patterns influence the distribution of food in the habitat, thus the abundance of aquatic and terrestrial food for the otters is therefore an important factor that is integral in determining the social and behavioral conducts of the predators. Among other factors that dictate the conduct of the otters are: the age of the otter, gender, and reproductive status (whether pregnant, lactating, etc.), physiological limitations, existence of predators like giant snakes, leopard etc. (Mumm, Urrutia & Knörnschild, 2014).

Vocalization in Otters

Vocalization is the process of producing sounds with the voice also may refer to the sound produced thereof. Nearly all otters produce audible sounds and can communicate to each other through a vocalizing frequently and with great volume. Earlier studies have been able distinguish at least nine different otter vocals from a simple screams that indicate from excitement, to coos connected with interaction. Generally, an otter would produce a high-pitched shout when troubled or when it’s interested in seeking attention, contented coos, as well as whines, whistles, growls, and snarls (Finerty et al., 2010).

Hypotheses

For this study we hypothesized the null hypothesis () as follows:

1. The average number of time spent foraging between the male and female otters are equal.
2. Weather elements greatly influence the average number of hours spent per otter foraging.
3. The average number of time spent by otters foraging dependent on gender.
4. Vocalization of otter significantly differs by Gender.

The alternative Hypothesis:

1. The average number of time spent foraging by the male otters is greater than female that the female.
2. Weather Elements (temperature) doesn’t in any way affect the average number of hours otters spend foraging.
3. The average number of time spent foraging in water is NOT dependent on gender
4. Vocalization doesn’t differ by Gender.

Methodology

We collected data from fourteen (14) small captive clawed adult otters at Melbourne Zoo; Australia thought to be a bonded pair. The pair was under surveillance for the entire seven (7) day period. The vocalizations of these otters were measured for the entire time period as well during the time intervals 9AM-12:30 PM & 1 PM 4:30PM where a 1 hour continuous observation followed by a minimum 15-30 minute break before second hour of observation. A critical significance level of P=0.05 was used for interpretation of the rejection region.

The subsequent data analysis procedure adopted for this study included, frequency of occurrence (FO) of the given variables (this is the proportion of the total number of samples examined, expressed as a percentage). Further a student t-test and Chi-square was introduced to calculate each of the outlined Hypotheses. The outcomes of the analysis were compared with evidence on from previous studies and the relevant conclusion drawn.

Results

Table 1 Sample Descriptive of the variables

Descriptive Statistics: Sample

Variable Gender Mean SE Mean StDev Median

Total observation time Female 92.3 17.4 46.0 75.0

Male 92.3 17.4 46.0 75.0

Number of vocalizations Female 1.286 0.969 2.563 0.000

Male 167.7 61.0 161.4 124.0

Time spent in water (min) Female 12.57 1.94 5.13 12.00

Male 8.29 1.68 4.45 9.00

Time spent on land (min) Female 78.3 16.3 43.0 63.5

Male 75.3 18.9 50.1 69.0

Time spent foraging (min Female 21.86 4.99 13.21 17.00

Male 17.21 4.79 12.67 15.00

The sample data was analyzed and the descriptive summary of the variables is represented in table 1, the gender-wise descriptive summary for the total observation time, the 14 male participants had a mean time of 92.3(SD = 46.0). The total times of 60.0, 75.0, and 124.0 represented the 25th, 50th, and 75th percentiles, respectively. On the other hand, the female total observation time had the mean, standard deviation and percentiles equal to those of the male.

A two sample t-test showed that the difference in average number of time spent by otters foraging in water (n =14, M = 10.43, SD = 5.12) and the time on land (n = 14, M = 76.8, SD = .44.9) were statistically significant, t (13) = -5.50, p