Intrinsic and extrinsic drivers of shape variation in the albatross compound bill

Albatross are the largest seabirds on Earth and have a suite of adaptations for their pelagic lifestyle. Rather than having a bill made of a single piece of keratin, Procellariiformes have a compound rhamphotheca, made of several joined plates. Drivers of the shape of the albatross bill have not been explored. Here we use three-dimensional scans of 61 upper bills from 12 species of albatross to understand whether intrinsic (species assignment & size) or extrinsic (diet) factors predict bill shape. Diet is a significant predictor of bill shape with coarse dietary categories providing higher R2 values than dietary proportion data. We also find that of the intrinsic factors, species assignment accounts for ten times more of the variation than size (72% versus 6.8%) and that there is a common allometric vector of shape change between all species. When considering species averages in a phylogenetic framework, there are significant Blomberg's K results for both shape and size (K = 0.29 & 1.10) with the first axis of variation having a much higher K value (K = 1.9), reflecting the split in shape at the root of the tree. The influence of size on bill shape is limited, with species assignment and diet predicting far more of the variation. The results show that both intrinsic and extrinsic factors are needed to understand morphological evolution.

Albatrosses develop attraction to fishing vessels during immaturity but avoid them at old age

Animals have to develop novel behaviours to adapt to anthropogenic activities or environmental changes. Fishing vessels constitute a recent feature that attracts albatrosses in large numbers. While they provide a valuable food source through offal and bait, they cause mortalities through bycatch, such that selection on vessel attraction will depend on the cost-benefit balance. We examine whether attraction to fishing and other vessels changes through the lifetime of great albatrosses, and show that attraction differed between age classes, sexes and personality. Juveniles encountered fewer vessels than adults, but also showed a lower attraction to vessels when encountered. Attraction rates, especially for fishing vessels, increased through immaturity to peak during adulthood, decreasing with old age. Shy females had lower attraction to vessels and shy males remained at vessels longer, suggesting that bolder individuals may outcompete shyer ones, with positive consequences for mass gain. These results suggest that attraction to vessels is a learned process, leading to an increase with age, and is not the result of preferential attraction to new objects by juveniles. Overall, our findings have important conservation implications as a result of potential strong differential selection on the risk of bycatch for age classes, personality types, populations and species.

A novel hypothesis for how albatrosses optimize their flight physics in real-time: an extremum seeking model and control for dynamic soaring

The albatross optimized flight maneuver-known as dynamic soaring-is nothing but a wonder of biology, physics, and engineering. By utilizing dynamic soaring, this fascinating bird can travel in the desired flight direction almost for free by harvesting energy from the wind. This phenomenon has been observed for centuries as evidenced by the writings of Leonardo da Vinci and Lord Rayleigh. Moreover, dynamic soaring biological inspiration has triggered a momentous interest among many communities of science and engineering, particularly aeronautical, control, and robotic engineering communities. That is, if dynamic soaring is mimicked, we will have arrived at a new class of unmanned aerial vehicles that are very energy-efficient during part (or the full) duration of their flight. Studying, modeling, and simulating dynamic soaring have been conducted in literature by mostly configuring dynamic soaring as an optimal control problem. Said configuration requires accurate dynamic system modeling of the albatross/mimicking-object, accurate wind profile models, and a defined mathematical formula of an objective function that aims at conserving energy and minimizing its dissipation; the solution then of such optimal control problem is the dynamic soaring trajectory taken-or to be taken-by the bird/mimicking-object. Furthermore, the decades-long optimal control configuration of the dynamic soaring problem resulted in non-real-time algorithms and control solutions, which may not be aligned well with the biological phenomenon itself; experimental observations of albatrosses indicate their ability to conduct dynamic soaring in real-time. Indeed, a functioning modeling and control framework for dynamic soaring that allows for a meaningful bio-mimicry of the albatross needs to be autonomous, real-time, stable, and capable of tolerating the absence of mathematical expressions of the wind profiles and the objective function-hypothetically similar to what the bird does. The qualifications of such modeling and control framework are the very same characteristics of the so-called extremum seeking systems. In this paper, we show that extremum seeking systems existing in control literature for decades are a natural characterization of the dynamic soaring problem. We propose an extremum seeking modeling and control framework for the dynamic soaring problem hypothesizing that the introduced framework captures more features of the biological phenomenon itself and allows for possible bio-mimicking of it. We provide and discuss the problem setup, design, and stability of the introduced framework. Our results, supported by simulations and comparison with optimal control methods of the literature, provide a proof of concept that the dynamic soaring phenomenon can be a natural expression of extremum seeking. Hence, dynamic soaring has the potential to be performed autonomously and in real-time with stability guarantees.

Environmental variability directly affects the prevalence of divorce in monogamous albatrosses

In many socially monogamous species, divorce is a strategy used to correct for sub-optimal partnerships and is informed by measures of previous breeding performance. The environment affects the productivity and survival of populations, thus indirectly affecting divorce via changes in demographic rates. However, whether environmental fluctuations directly modulate the prevalence of divorce in a population remains poorly understood. Here, using a longitudinal dataset on the long-lived black-browed albatross (Thalassarche melanophris) as a model organism, we test the hypothesis that environmental variability directly affects divorce. We found that divorce rate varied across years (1% to 8%). Individuals were more likely to divorce after breeding failures. However, regardless of previous breeding performance, the probability of divorce was directly affected by the environment, increasing in years with warm sea surface temperature anomalies (SSTA). Furthermore, our state-space models show that warm SSTA increased the probability of switching mates in females in successful relationships. For the first time, to our knowledge, we document the disruptive effects of challenging environmental conditions on the breeding processes of a monogamous population, potentially mediated by higher reproductive costs, changes in phenology and physiological stress. Environmentally driven divorce may therefore represent an overlooked consequence of global change.

Effects of El Niño-driven changes in wind patterns on North Pacific albatrosses

Changes to patterns of wind and ocean currents are tightly linked to climate change and have important implications for cost of travel and energy budgets in marine vertebrates. We evaluated how El Niño-Southern Oscillation (ENSO)-driven wind patterns affected breeding Laysan and black-footed albatross across a decade of study. Owing to latitudinal variation in wind patterns, wind speed differed between habitat used during incubation and brooding; during La Niña conditions, wind speeds were lower in incubating Laysan (though not black-footed) albatross habitat, but higher in habitats used by brooding albatrosses. Incubating Laysan albatrosses benefited from increased wind speeds during El Niño conditions, showing increased travel speeds and mass gained during foraging trips. However, brooding albatrosses did not benefit from stronger winds during La Niña conditions, instead experiencing stronger cumulative headwinds and a smaller proportion of trips in tailwinds. Increased travel costs during brooding may contribute to the lower reproductive success observed in La Niña conditions. Furthermore, benefits of stronger winds in incubating habitat may explain the higher reproductive success of Laysan albatross during El Niño conditions. Our findings highlight the importance of considering habitat accessibility and cost of travel when evaluating the impacts of climate-driven habitat change on marine predators.

Optimal dynamic soaring consists of successive shallow arcs

Albatrosses can travel a thousand kilometres daily over the oceans. They extract their propulsive energy from horizontal wind shears with a flight strategy called dynamic soaring. While thermal soaring, exploited by birds of prey and sports gliders, consists of simply remaining in updrafts, extracting energy from horizontal winds necessitates redistributing momentum across the wind shear layer, by means of an intricate and dynamic flight manoeuvre. Dynamic soaring has been described as a sequence of half-turns connecting upwind climbs and downwind dives through the surface shear layer. Here, we investigate the optimal (minimum-wind) flight trajectory, with a combined numerical and analytic methodology. We show that contrary to current thinking, but consistent with GPS recordings of albatrosses, when the shear layer is thin the optimal trajectory is composed of small-angle, large-radius arcs. Essentially, the albatross is a flying sailboat, sequentially acting as sail and keel, and is most efficient when remaining crosswind at all times. Our analysis constitutes a general framework for dynamic soaring and more broadly energy extraction in complex winds. It is geared to improve the characterization of pelagic birds flight dynamics and habitat, and could enable the development of a robotic albatross that could travel with a virtually infinite range.

Longline fishing (how what you don't know can hurt you)

Longline fishing utilizes monofilament lines that can be as much as 62 miles long. The line itself is buoyed by Styrofoam or plastic floats. Usually, at about every 100ft, a secondary line is attached and hangs down from the mainline. The lines are baited with mackerel, squid, or shark meat and have as many as 10,000 hooks. Every 12-24 hours, the line is hauled in, mechanically rebaited, and set back into the water behind the vessel. The baited hooks can be seen by albatross and other seabirds as they are placed in the water or being hauled out. When the birds dive for the bait, they are hooked, dragged behind the fishing boat, and drown. Spectacularly nonselective, longline fishing techniques also hook many other forms of marine life-"bycatch" (sea turtles, seals, dolphins, penguins, sharks, and many other nontarget finfish). It is estimated that 300,000 seabirds (including 100,000 albatross) die on longlines each year. Albatross are among the longest-lived birds. They can live up to 60 years and some species do not start breeding until they are 10 years old. They have a low reproductive rate and many species only breed every other year. In addition, a species like the Wandering Albatross (Diomedea exulans) rears its chicks for an average of more than 270 days. Albatross pair for life and may take years to find a new partner if their mate is killed. Owing to their incredibly low reproductive rate, albatross are particularly vulnerable to longline fishing. Currently, it is believed that 4 albatross drown per 100,000 hooks set. This is more than 400 birds a week. The current mortality rate for adult birds is not sustainable and for some species, the birds are dying faster that they can repopulate. Currently, 19 of the world's 22 albatross species are threatened with extinction. This year longline fishing ships will set 10 billion hooks worldwide. Various mitigation measures (bird-scaring lines, weighted, faster-sinking line, setting lines deeper out of the bird's sight, reduction in the amount of offal discarded from fishing boats, night fishing, and restriction of longline operations from areas where nesting and foraging birds are congregated during the breeding season, among others) have been proposed and attempted. There is no one panacea for the effects of longlining and mitigation efforts are most successful when used in combination. Some of these mitigation measures have shown very promising results. Some experts feel that government legislation, regulation, and enforcement in conjunction with incentives for the fishing industry to incorporate and implement mitigating techniques have the best chance in ameliorating the problem. The public is surprisingly unaware of this wanton and wasteful exploitation of the ocean's resources, and the worldwide demand for seafood continues to rise. Meanwhile, globally, fishermen voice the same complaints: fewer fish, smaller fish, shorter fishing seasons, bizarre developments in their seasonal appearance and dispersal, and fewer overall species seen. These are all the classic signs of overfishing. Each year it is estimated that some 90 million tons of wild fish are harvested from our planet's oceans. Nearly 30 million tons of this is discarded as the incidental bycatch of nontarget species. If international curbs are not placed upon wasteful fishing practices, we are doomed to learn a painful maxim. "The ocean is not infinite." Veterinarians must become involved in worldwide conservation efforts, acting locally, while thinking globally.

Do naive juvenile seabirds forage differently from adults?

Foraging skills of young individuals are assumed to be inferior to those of adults. The reduced efficiency of naive individuals may be the primary cause of the high juvenile mortality and explain the deferment of maturity in long-lived species. However, the study of juvenile and immature foraging behaviour has been limited so far. We used satellite telemetry to compare the foraging movements of juveniles, immatures and breeding adult wandering albatrosses Diomedea exulans, a species where foraging success is positively influenced by the distance covered daily. We showed that juveniles are able to use favourable winds as soon as the first month of independence, but cover shorter distances daily and spend more time sitting on water than adults during the first two months after fledging. These reduced movement capacities do not seem to be the cause of higher juvenile mortality. Moreover, juveniles almost never restrict their movement to specific areas, as adults and immatures frequently do over shelf edges or oceanic zones, which suggest that the location of appropriate areas is learned through experience. Immatures and adults have equivalent movement capacities, but when they are central place foragers, i.e. when adults breed or immatures come to the colony to display and pair, immatures make shorter trips than adults. The long duration of immaturity in this species seems to be related to a long period of learning to integrate the foraging constraints associated with reproduction and central place foraging. Our results indicate that foraging behaviour of young albatrosses is partly innate and partly learned progressively over immaturity. The first months of learning appear critical in terms of survival, whereas the long period of immaturity is necessary for young birds to attain the skills necessary for efficient breeding without fitness costs.

Why does the ocean sunfish bask?

Basking at the sea surface is a well known, but peculiar behavior of ocean sunfish (Mola mola). One of hypotheses for this behavior is parasite elimination. However, in oceanic regions, very little direct evidence exists for this form of interspecific communication. In pelagic waters of the North Pacific Ocean, we observed a school of 57 ocean sunfish, that were heavily infested around the base of their dorsal fins with the ecto-parasite Pennella sp. We photographed a Laysan albatross (Phoebastria immutabilis) nearby that picked a Pennella sp. from one of ocean sunfish and ate it. We hypothesize that ocean sunfish did “bask” to look for skin cleaning and that this symbiotic cleaning behavior by the albatrosses may be a common feature of the biology of the ocean sunfish. Here we provide more photographs to show heavy parasite infections and scars after parasite removal by “cleaners,” and discuss how important a symbiotic cleaning relationship could be in the open ocean ecosystem.