Efficient honey production requires knowledge about the behavior of the workers and the parameters that influence the strength of the colony. In this study, the objective was to analyze the interaction between the foraging behavior of worker honeybees and pollen storage levels in Africanized honeybees colonies. Colonies with low pollen storage increased pollen intake rates, but this value was 15% lower than colonies with high pollen storage, demonstrating a direct relationship between the pollen storage levels and foraging activity. The difference in pollen intake rates varied according to the number of foraging honeybees and pollen load collected by each individual. Under both high and low pollen storage, colonies returned pollen storage to initial level within 16 days, suggesting that honeybees regulate pollen storage levels around a homeostatic set point. Relationship between pollen storage levels and colony brood production was also found, indicating how alterations in the behavior of each individual can affect the strength of the colony.
Foraging behavior of Apis mellifera is extremely important to the colony development. Under normal colony conditions, the forager honeybees are workers with an age of over 21 days, at which time they shift to perform tasks outside of the hive, including water, nectar, pollen or resin collection [
Forager honeybees can be classified into two categories: scout honeybees which search for the best food resource and the reticent honeybees which wait in the beehive until the scout honeybees return and give them information about the food source by dancing [
Understanding the foraging behavior is important for understanding the biology of the honeybee and it is essential to improve management techniques. However, there are very few studies about foraging decisions when changes occur in the colony. Given these characteristics, this research was carried out to study the foraging behavior of Apis mellifera Africanized honeybees with changes in the amount of pollen stored in the colony.
The study was conducted in December 2014, at Experimental Farm of Iguatemi, belonging to the State University of Maringa. Six colonies of Apis mellifera Africanized honeybees were used, each colony contained approximately 25.000 adult honeybees kept in Langstroth hives. The observations of foraging occurred during 16 days.
Initially colonies were mapped and standardized according to the method adapted from Al-Tikrity et al. (1971) [
To observe the relationship between the pollen storage level and foraging behavior, two manipulations were performed by removing or adding pollen combs in the colony. The first group consisted of three colonies with high amount of stored pollen (973 cm2) and the second group three colonies with low amount of stored pollen (52 cm2).
Regarding the amount of pollen stored in the colony, it was observed by mapping in the first, eighth and sixteenth days, being the first day for standardization, eighth and sixteenth days to observe the colony of pollen storage behavior. Rates of foragers collecting pollen and other foragers were observed in the entrance of the hive of both groups during five minutes, every other day, at 9.00 am.
To verify the forage for pollen load per forager a set of tem pollen foragers per colony was used, these foragers were collected in the entrance of the colony with the aid of an entomological aspirator in the four-day break. In the laboratory the pollen load was removed from the corbiculae of these forages to determine fresh and dry weight. The loads were weighed on an analytical balance, placed in an oven at 42˚C for three days and weighed again.
The pollen entrance rate was measured by inserting pollen collectors in the entrance in the third and eighth day of the experiment, for an hour. Pollens were removed from the drawers, placed in plastic bags, identified in the laboratory and analyzed the wet and dry weight as described above.
Climatic data of the maximum and minimum temperature (˚C), relative maximum and minimum humidity of air (%) and sum of precipitation (mm) were obtained through Climatological Station of the Experimental Farm of Iguatemi, State and Maringa University.
Data were statistically analyzed using the procedure generalized linear models-proc GLM (General Linear Models) of the statistical package SAS (2013) [
After the manipulation of the colonies there was a significant difference between the means of pollen areas (cm2) in hives with high (973 cm2) and low (52 cm2) initial amount of pollen (
The colonies with low pollen storage, eight days after the manipulation managed to increase the stored pollen area from 52 cm2 to 160 cm and after 16 days presented an average of 85 cm2. While colonies with high of pollen storage decreased the area of 973 cm2 to 261 cm2; and 16 days after the manipulation the average area stocked with pollen was 188 cm2.
A higher number of pollen forager honeybees were observed at 9.00 am. There was no significant difference between the average number of foragers for pollen, other foragers or total of forager honeybees in colonies with high or low amount of initial pollen. Colonies with high storage pollen presented higher pollen load entering per hour (1.97 g/h), when compared to colonies with low storage pollen (1.25 g/h). There was no significant difference between means of fresh pollen load and dry pollen load weight taken from the pollen basket.
During the experimental period the average minimum external temperature was 20.0˚C and the maximum was 27.9˚C. Regarding precipitation, it rained rainfall was only one day and it was 2.4 mm.
The amount of stored pollen changed in both groups (
The decrease or stimulating of pollen foraging activity in response to addition or removal of it in the colony was also observed by [
Colony | 8˚ day | 16˚ day |
---|---|---|
High pollen storage | 261a | 188a |
Low pollen storage | 160a | 85b |
Means followed by different letters in the same column are significantly different (P < 0.05).
Initially colonies were standardized with average pollen area of 48,867 cm2 and none returned to baseline, but were left with values close to each other at 16 days after manipulation. Possibly, colonies regulate pollen storage rate based on a set point. This point may be related to floral resources available at the time and the number of uncapped brood within the colony [
The foraging period of Apis mellifera honeybees may vary due to numerous factors, may start early in the morning and finish in the evening. Joshi e Joshi (2010) [
The foraging activity or floral visitation is analyzed using different parameters, such as foraging commencement or/and cessation time [
Colonies with high storage pollen presented higher pollen load entering per hour (1.97 g/h), when compared to colonies with low storage pollen (1.25 g/h), which represents a difference of approximately 58% between groups. Colonies with high storage pollen had a mean fresh pollen load weight taken from the pollen basket of 36.43 mg, and dry weight 24.68 mg. While colonies with low pollen storage had a mean fresh weight of 39.40 mg and dry weight 26.81 mg. Pollen loads after removing the humidity was approximately 32% lighter than the fresh load in both groups.
Colonies with high pollen reserves presented higher pollen entry due to large amount of foragers honeybees, 15% more, but managed to reduce pollen in the colony area decreasing the size of pollen load by forager. While colonies with low pollen reserves increases the stored pollen area, increasing the size of load per trip, despite having lower quantity of forager honeybees collecting pollen. Free (1967) [
load weight in 19%.
In a study conducted in Africanized honeybees, Seeley (1995) [
During the experimental period the average minimum external temperature was 20.0˚C and the maximum was 27.9˚C. Joshi and Joshi (2010) [
The experiment was conducted during the summer season when there is plenty of pollen in the assessed region, which possibly allowed the colonies with low pollen storage increase pollen entrance rate in a short time. The quality of pollen available in the area is also an important factor in foraging rate, Pernal and Currie (2001) [
Moreover, if the beekeeper is looking for high pollen production, establishing a genetic breeding program is a key factor to improve the results. Page and Fondrk (1995) [
Honeybees stored the amount of pollen needed to maintain the colony brood by changing the foraging behavior according to the amount of pollen stocked. As the colonies were standardized in population and were located in the same area, there was no difference in forager honeybee number and amount of pollen collected between colonies with high and low pollen stocked initially. Colonies increased or decreased the number stored pollen area according to the colony conditions.
To National Council of Scientific and Technological Development (CNPq, Brazil), process 308283/2011 and 311663/2014-1 for financial support.
Erica Gomes de Lima,Simone Cristina Camargo,Pedro da Rosa Santos,Jose Washington Santos Oliveira,Vagner de Alencar Arnaut de Toledo, (2016) Regulation of Pollen Foraging Activity in Apis mellifera Africanized Honeybees Colonies. Agricultural Sciences,07,335-340. doi: 10.4236/as.2016.76034