Annual Fluctuations in Winter Colony Losses of Apis mellifera L. Are Predicted by Honey Flow Dynamics of the Preceding Year.

Winter loss rates of honey bee colonies may fluctuate highly between years in temperate climates. The present study combined survey data of autumn and winter loss rates in Germany (2012-2021) with estimates of honey flow-assessed with automated hive scales as the start of honey flow in spring and its magnitude in summer-with the aim of understanding annual fluctuations in loss rates. Autumn colony loss rates were positively and significantly correlated with winter loss rates, whereas winter loss rates were inversely related to loss rates in autumn of the following year. An early start of net honey flow in spring predicted high loss rates in both autumn and winter, whereas high cumulative honey flow led to lower loss rates. The start of net honey flow was related to temperature sums in March. Combined, the results implied that the winter loss rate in one year was influenced by the loss rate of the preceding winter and shaped by honey flow dynamics during the following year. Hence, the rate of colony loss in winter can be viewed as a cumulative death process affected by the preceding one and a half years.

Maternal mouth-to-mouth feeding behaviour in flower-visiting bats, but no experimental evidence for transmitted dietary preferences.

In addition to breast milk, several mammals feed their offspring with primary food items. This provisioning can offer both energetic and informational benefits: young might use parentally provided food as a source of nutrients, but also as a valuable option to socially learn about adults' food. For bats, there are only very few and partially anecdotal reports of adults feeding their pups with primary food, and there is also a lack of information about social learning processes during ontogeny. In the present study, we provide experimental evidence that lactating flower-visiting bats (Glossophaga soricina) provide regurgitated nectar via mouth-to-mouth feeding behaviour to their pups. After licking at their mothers' slightly opened mouth, pups defecated a marker substance that was exclusively available in the mothers' nectar diet. We additionally investigated associated informational benefits by testing for a social transmission of dietary preferences. We experimentally induced a dietary preference for specifically flavoured nectars to mothers with non-volant pups. Subsequently, after pups became volant, we tested their dietary preferences in a choice experiment. However, we found no experimental evidence that pups adopted the preferences of their mothers.

The predictive start of hunting archer fish: a flexible and precise motor pattern performed with the kinematics of an escape C-start.

Once their shots have successfully dislodged aerial prey, hunting archer fish monitor the initial values of their prey's ballistic motion and elicit an adapted rapid turning maneuver. This allows these fish to head straight towards the later point of catch with a speed matched to the distance to be covered. To make the catch despite severe competition the fish must quickly and yet precisely match their turn and take-off speed to the initial values of prey motion. However, the initial variables vary over broad ranges and can be determined only after prey is dislodged. Therefore, the underlying neuronal circuitry must be able to drive a maneuver that combines a high degree of precision and flexibility at top speed. To narrow down which neuronal substrate underlies the performance we characterized the kinematics of archer fish predictive starts using digital high-speed video. Strikingly, the predictive starts show all hallmarks of Mauthner-driven teleost C-type fast-starts, which have previously not been noted in feeding strikes and were not expected to provide the high angular accuracy required. The high demands on flexibility and precision of the predictive starts do not compromise their performance. On the contrary, archer fish predictive starts are among the fastest C-starts known so far among teleost fish, with peak linear speed beyond 20 body lengths s(-1), angular speed over 4500 deg. s(-1), maximum linear acceleration of up to 12 times gravitational acceleration and peak angular acceleration of more than 450 000 deg. s(-2). Moreover, they were not slower than archer fish escape C-starts, elicited in the same individuals. Rather, both escapes and predictive starts follow an identical temporal pattern and all kinematic variables of the two patterns overlap. This kinematic equivalence strongly suggests that archer fish recruit their C-start escape network of identified reticulospinal neurons, or elements of it, to drive their predictive starts. How the network drives such a rather complex behavior without compromising speed is a wide open question.

Animal cognition: how archer fish learn to down rapidly moving targets.

In extremely rapid maneuvers, animals including man can launch ballistic motor patterns that cannot immediately be corrected. Such patterns are difficult to direct at targets that move in three-dimensional space, and it is presently unknown how animals learn to acquire the precision required. Archer fish live in groups and are renowned for their ballistic hunting technique in which they knock down stationary aerial insect prey with a precisely aimed shot of water. Here we report that these fish can learn to release their shots so as to hit prey that moves rapidly at great height, a remarkable accomplishment in which the shooter must take both the target's three-dimensional motion as well as that of its rising shot into account. To successfully perform in the three-dimensional task, training with horizontal motion suffices. Moreover, all archer fish of a group were able to learn the complex sensomotor skill from watching a performing group member, without having to practice. This instance of social learning in a fish is most remarkable as it could imply that observers can "change their viewpoint," mapping the perceived shooting characteristics of a distant team member into angles and target distances that they later must use to hit.

Hunting archer fish match their take-off speed to distance from the future point of catch.

Archer fish can shoot down insect prey with a sharp jet of water. Fish usually fire from positions that are not directly below their target so that a dislodged insect falls ballistically with a horizontal velocity component. Only 100 ms after the insect is on its path both the shooter and other school members can initiate a rapid turn and then head straight in the direction of the later point of impact of their falling prey. The quick turn and subsequent take-off are performed ;open-loop', based on the initial values of the falling insect's motion. We report here that archer fish can not only take off in the direction of the later point of impact but also predict its distance. Distance information allows the fish to adjust their take-off speed so that they would arrive within a narrow time slot slightly (about 50 ms) after their prey's impact, despite large differences in the size of the aligning turn and in the distance to be covered. Selecting a constant speed program with matched speed and catching the insect on the move minimizes frictional losses. The initial speed of starting fish is slightly but systematically too slow and is increased later so that the fish arrive 20 ms earlier than expected and often make the catch on a higher than take-off speed. The variability of later speed changes suggests a systematic ;error' in the take-off, as if the fish underestimated distance. However, this apparent deficiency seems well adapted to the fish catching their prey at a high speed: if later the fish had no possibility to correct an initial error then it is better to start slightly too slow in order to minimize the risk of overshooting the point of catch.