Floral Traits Predict Frequency of Defecation on Flowers by Foraging Bumble Bees

Flowers may become inoculated with pathogens that can infect bees and other critical pollinators, but the mechanisms of inoculation remain unclear. During foraging, bees may regurgitate or defecate directly onto flower parts, which could inoculate flowers with pollinator pathogens and lead to subsequent disease transmission to floral visitors. We tested if captive eastern bumble bees (Bombus impatiens) (Cresson) (Hymenoptera: Apidae) defecate on floral surfaces during foraging and if flower shape played a role in the probability of defecation and the quantity of feces deposited on floral surfaces. Captive Bombus impatiens were fed a solution of fluorescent dye and sucrose, then allowed to forage freely on flowers of a variety of shapes in a flight cage. Flowers were then examined under ultraviolet light for fluorescing fecal matter. We found that bumble bees did defecate on floral surfaces during foraging and that composite flowers with a large area of disk flowers were the most likely to have feces on them. Our results point to defecation by bumble bees during foraging as a potential mechanism for inoculation of flowers with pollinator pathogens and suggest that flower shape could play a significant role in inoculation.

Flights of a Multirotor UAS with Structural Faults: Failures on Composite Propeller(s)

Data acquired from several flights of a custom-fabricated Hexacopter Unmanned Aerial System (UAS) with composite structure (carbon fiber arms and central hub) and composite (carbon fiber) propellers are described in this article. The Hexacopter was assembled from a commercially available kit (Tarot 690) and flown in manual and autonomous modes. Takeoffs and landings were under manual control and the bulk of the flight tests was conducted with the Hexacopter in a “position hold” mode. All flights were flown within the UAS flight cage at Parks College of Engineering, Aviation and Technology at Saint Louis University for approximately 5 min each. Several failure conditions (different types, artificially induced) on the composite (carbon fiber) propellers were tested, including failures on up to two propellers. The dataset described in this article contains flight data from the onboard flight controller (Pixhawk) as well as three accelerometers, each with three axes, mounted on the arms of the Hexacopter UAS. The data are included as supplemental material.

Hummingbird foraging preferences under natural and experimental conditions

Background. Different studies have assessed hummingbirds’ preferences for feeding resources, mainly according to floral characteristics such as shape, color, and morphology, in addition to the nectar concentration, quantity, and sugar composition of flowers visited. Flower preferences can also depend on hummingbirds’ life history with respect to flower use. Hence, latitudinal migrant hummingbirds likely differ from resident species as they are accustomed to using a wider range of resources. In this study, we assessed the flower preferences of a migrant and a resident species that are common during winter in northern Mexico using both observational and experimental methods. Methods. We assessed hummingbird preferences for the most common plant species in the study region. In particular, we compared the preferences of two common hummingbird species, one resident (Amazilia beryllina) and one latitudinal migrant (Selasphorus rufus), for the most regionally common plant species, Cestrum thyrsoideum and Salvia iodantha, which have different color flowers yet produce similar energetic rewards. We calculated the Jacob selectivity index from preference data obtained under natural field conditions and with a flight cage in order to evaluate specific interactions. Results: Both hummingbird species showed different visitation rates to the studied plants under natural conditions in the study site. A. beryllina visited the yellow flowers of C. thyrsoideum more frequently, while S. rufus visited the fuchsia flowers of S. iodantha with greater frequency. In the flight cages, both species preferred the fuchsia flowers of S. iodantha when presented in similar or lesser abundance than the yellow flowers. Discussion. Under natural conditions, A. beryllina visited C. thyrsoideum to a greater extent in comparison with S. iodantha yet preferred S. iodantha in the flight cage when other hummingbirds were absent and even when S. iodantha was not the most abundant species. This could confirm that competition is an important process that drives the niche displacement of A. beryllina. On the other hand, the latitudinal migratory species S. rufus maintained its preferences for flowers of a familiar color under both natural and experimental conditions. Conclusions. Our results showed that the feeding preferences of the studied hummingbird species depend on the life history of each species. Therefore, the response of these migratory hummingbird species to feeding resources and possible exclusion from their preferred resources depends on their type of migration, territoriality, and possible associations with local plants.

Hummingbird foraging preferences under natural and experimental conditions

Background. Different studies have assessed hummingbirds’ preferences for feeding resources, mainly according to floral characteristics such as shape, color, and morphology, in addition to the nectar concentration, quantity, and sugar composition of flowers visited. Flower preferences can also depend on hummingbirds’ life history with respect to flower use. Hence, latitudinal migrant hummingbirds likely differ from resident species as they are accustomed to using a wider range of resources. In this study, we assessed the flower preferences of a migrant and a resident species that are common during winter in northern Mexico using both observational and experimental methods. Methods. We assessed hummingbird preferences for the most common plant species in the study region. In particular, we compared the preferences of two common hummingbird species, one resident (Amazilia beryllina) and one latitudinal migrant (Selasphorus rufus), for the most regionally common plant species, Cestrum thyrsoideum and Salvia iodantha, which have different color flowers yet produce similar energetic rewards. We calculated the Jacob selectivity index from preference data obtained under natural field conditions and with a flight cage in order to evaluate specific interactions. Results: Both hummingbird species showed different visitation rates to the studied plants under natural conditions in the study site. A. beryllina visited the yellow flowers of C. thyrsoideum more frequently, while S. rufus visited the fuchsia flowers of S. iodantha with greater frequency. In the flight cages, both species preferred the fuchsia flowers of S. iodantha when presented in similar or lesser abundance than the yellow flowers. Discussion. Under natural conditions, A. beryllina visited C. thyrsoideum to a greater extent in comparison with S. iodantha yet preferred S. iodantha in the flight cage when other hummingbirds were absent and even when S. iodantha was not the most abundant species. This could confirm that competition is an important process that drives the niche displacement of A. beryllina. On the other hand, the latitudinal migratory species S. rufus maintained its preferences for flowers of a familiar color under both natural and experimental conditions. Conclusions. Our results showed that the feeding preferences of the studied hummingbird species depend on the life history of each species. Therefore, the response of these migratory hummingbird species to feeding resources and possible exclusion from their preferred resources depends on their type of migration, territoriality, and possible associations with local plants.

A comparison of the effectiveness of methods of deterring pteropodid bats from feeding on commercial fruit in Madagascar

We compared the effectiveness of methods of deterring Pteropus rufus from feeding on commercial fruit in east central and southeastern Madagascar in 2012–2013 during the Litchi chinensis harvest. Two of the three methods used, installing plastic flags and ringing bells in the trees, were derived from those used by litchi growers in the southeast. We improved and standardized these methods and compared their effectiveness with an organic product made from dried blood and vegetable oil (Plantskydd®) with a taste and odour aimed at deterring mammal feeding. The bats damaged from 440–7,040 g of litchi fruits per tree and two of the three methods reduced the fruit lost to bats: the plastic flags and the organic deterrent. There were significant differences in the damage levels between the study sites and between our three methods of deterrence. The plastic flags and bell ringing methods were significantly less effective in reducing the fruit bat damage compared to the taste deterrent. The latter was most effective when it had enough time to dry and adhere to the fruits after spraying and before rain. Its effectiveness was further demonstrated in flight cage experiments during which Rousettus madagascariensis avoided litchis treated with Plantskydd®. Analysis of bat faecal samples revealed no feeding preference but the collected samples contained large numbers of Ficus seeds, suggesting that the bats feed extensively on Ficus fruits rather than on fruit of economic importance. Apart from fruit ripeness, tree productivity or other phenological factors did not affect the amount of fruit eaten by the bats. More fruits were damaged by birds than bats at both study sites.

Bees do not use nearest-neighbour rules for optimization of multi-location routes

Animals collecting patchily distributed resources are faced with complex multi-location routing problems. Rather than comparing all possible routes, they often find reasonably short solutions by simply moving to the nearest unvisited resources when foraging. Here, we report the travel optimization performance of bumble-bees ( Bombus terrestris ) foraging in a flight cage containing six artificial flowers arranged such that movements between nearest-neighbour locations would lead to a long suboptimal route. After extensive training (80 foraging bouts and at least 640 flower visits), bees reduced their flight distances and prioritized shortest possible routes, while almost never following nearest-neighbour solutions. We discuss possible strategies used during the establishment of stable multi-location routes (or traplines), and how these could allow bees and other animals to solve complex routing problems through experience, without necessarily requiring a sophisticated cognitive representation of space.

Going to great lengths: selection for long corolla tubes in an extremely specialized bat–flower mutualism

In a hypothesis that has remained controversial since its inception, Darwin suggested that long-tubed flowers and long-tongued pollinators evolved together in a coevolutionary race, with each selecting for increasing length in the other. Although the selective pressures that flowers impose on tongue length are relatively straightforward, in that longer tongues allow access to more nectar, selective pressures that pollinators impose on flower length are less clear. Here, we test for such selective pressures in the highly specialized mutualism between the nectar bat Anoura fistulata , which can extend its tongue twice as far as other nectar bats, and Centropogon nigricans , which has flowers of a similar length (8–9 cm). We used flight cage experiments to examine the effects of artificially manipulated flower lengths on (i) bat behaviour and (ii) pollen transfer. Increased length produced longer visits, but did not affect the force bats applied during visits. In the second experiment, flower length increased both the male and female components of flower function: long male flowers delivered more pollen grains and long female flowers received more pollen grains. However, pollen transfer was not correlated with visit duration, so the mechanism behind differences in pollen transfer remains unclear. By demonstrating that bats select for increasing flower length, these results are consistent with the hypothesis that A. fistulata evolved its remarkable tongue in a coevolutionary race with long-tubed flowers similar to that envisioned by Darwin.