Foraging currencies for non-energetic resources: pollen collection by bumblebees

• Published in: Animal behaviour Vol. 54; no. 4; pp. 911 - 926
• Main Authors: RASHEED, SALMAN A, HARDER, LAWRENCE D
• Format: Journal Article
• Language: English
• Published: Kent Elsevier Ltd 01.10.1997; Elsevier; Harcourt Brace Jovanovich Ltd
• Subjects: Animal behavior; Animal ethology; Bees; Biological and medical sciences; Bombus; collection; efficiency; foraging; Fundamental and applied biological sciences. Psychology; Lupinus; optimization; Pollen; Protozoa. Invertebrata; Psychology. Psychoanalysis. Psychiatry; Canada; British Columbia; Alberta; North America; America; Feeding behavior; Insecta; Apidae; Cost benefit analysis; Modeling; Foraging behavior; Bombus; Energy balance; Apoidea; Arthropoda; Pollen; Hymenoptera; Invertebrata; Mathematical model; Aculeata; Field study
• ISSN: 0003-3472; 1095-8282
• DOI: 10.1006/anbe.1997.0487

Animals sometimes forage for resources whose benefits are not energy-based. In such cases, the benefits and costs of foraging cannot be directly compared, making it difficult to evaluate the currency of fitness maximized by the animal's behaviour. For bees, pollen represents such a resource, because they collect pollen as the sole protein source for developing larvae, rather than as a source of energy. This study compared three currencies that could be maximized during pollen collection by bumblebees (Bombusspp.) foraging on different lupin species (Lupinusspp.): pollen collected per inflorescence, pollen collection rate (gross benefits/time) and pollen collection efficiency (gross benefits/costs). Bees visiting lupin inflorescences begin foraging low on an inflorescence and then move upward through a gradient of increasing pollen availability. To maximize each currency, we predicted that a bee would begin foraging at a different position along a lupin inflorescence, depending on the relative influences of the time and energy costs associated with handling flowers and flight. Based on comparisons of observed and predicted starting positions for seven situations, maximization of gross pollen-collection efficiency predicted observed behaviour better than either pollen collected per inflorescence or gross rate of pollen collection. Such maximization of pollen-collection efficiency would enhance a bee's lifetime input of pollen to her colony, as has been demonstrated for nectar-collecting bees. Hence, the economics of foraging for non-energetic resources do not differ qualitatively from foraging for energy.