Energetically Pricey Lifestyles and Low Productivity Environments: How the Galapagos Sea Lion Makes Ends Meet

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Energetically Pricey Lifestyles and Low Productivity Environments: How the Galapagos Sea Lion Makes Ends Meet

November 30, 2017/0 Comments/in Conservation, Ocean News /by aanstett

By Patricia Albano, SRC Intern

Metabolic rate and prey acquisition behavior can be revealing factors in studies examining physiological adaptations to unpredictable environments. Specifically, otariids (sea lions and fur seals) display an energetically expensive lifestyle due to their high costs of thermoregulation which can provide challenges in equatorial regions such as the Galapagos where resources are limited and unpredictable. In this study (conducted by Stella Villegas-Amtmann et. al, 2016), the effect of the Galapagos islands’ low productivity on the Galapagos sea lion (GSL) (Image 1) is explored. To determine how sea lions maintain their energetically expensive lifestyle in limiting environments, researchers measured the field metabolic rate (FMR) and the foraging behavior of lactating female sea lions rearing pups and yearlings. Because lactation is the most energetically costly time in a female mammal’s life history (Hammond and Diamond, 1997; Williams et. al, 2007), the researchers hypothesized that GSL would exhibit a lower FMR in relation to other species as a response to decreased resource availability (Trillmich and Kooyman, 2001), but lactating GSLs rearing yearling pups would display greater FMRs and foraging efforts than those rearing younger pups (~1 year old). This hypothesis was drawn based on literature that suggests that there is a positive relationship between female energy expenditure and pup mass/age before the weaning period at ~3 years of age (Jeglinski et al., 2012; Trillmich, 1986a).

Suckling Galapagos sea lion (Zalophus wollebaeki) pup and lactating mother. Source: Wikimedia Commons.

This research was carried out at San Cristobal Island during October and November of 2009. 10 lactating female GSLs and their pups/yearlings were caught using hoop nets. Of the 10 pups, 6 were suckling young pups (~ 1 month old) and the other 4 were suckling yearlings. To analyze prey acquisition behavior, the animals were fitted with GPS tags, time-depth recorders, and radio transmitters. For each sea lion, the researchers calculated % shallow dives (100m depth), mean depths for shallow and deep dives, dive duration, bottom time, maximum distance traveled from the rookery, and time spent diving. Results show that GSLs with yearlings dove further, deeper, and longer than GSLs with younger pups (Table 1). The field metabolic rate measurement of the seals exhibited the same relationship: females with yearlings had a higher FMR than those with young pups. These results confirm the researchers’ hypothesis that GSLs with yearling pups would have a more energetically costly lifestyle than females with younger pups.

Galapagos sea lion females’ foraging location, maximum dive parameters, and mean foraging trip parameters. This table includes the age categories of the females’ pups so the relationship between pup age and energy expending activities can be seen. Source: Villegas-Amtmann, S., et al., Adapted to change: Low energy requirements in a low and unpredictable productivity environment, the case of the Galapagos sea lion. Deep-Sea Res. II (2016).

This study shows a remarkable ability of sea lions to reduce their metabolic needs to adapt to the low productivity ecosystem of the Galapagos islands. However, while this species shows an impressive plasticity in responding to environmental changes, in comparison to other higher latitude ostariids, endangered GSLs live in an environment that requires them to exert a significantly greater amount of effort in order to maintain their and their offspring’s metabolism. If warming trends in equatorial waters continue and productivity in the Galapagos proceeds to decrease (Bopp et al., 2013), GSLs already functioning at their lower physiological limit may not be able to adapt further.

Works Cited

Hammond, K.A., Diamond, J., 1997. Maximal sustained energy budgets in humans and animals. Nature 386 (6624), 457–462.

Trillmich, F., Kooyman, G.L., 2001. Field metabolic rate of lactating female Galapagos fur seals (Arctocephalus galapagoenis): the influence of offspring age and environment. Comp. Biochem. Phys. A 129 (4), 741–749.

Trillmich, F., 1986a. Attendance behavior of Galapagos sea lions. In: Gentry, R.L., Kooyman, G.L. (Eds.), Fur Seals: Maternal Strategies on Land and at Sea. Princeton University Press, Princeton, New Jersey, pp. 196–208.

Villegas-Amtmann, S., et al., Adapted to change: Low energy requirements in a low and unpredictable productivity environment, the case of the Galapagos sea lion. Deep-Sea Res. II (2016), http://dx.doi.org/10.2016/j.dsr2.2016.05.015

Williams, T.M., Rutishauser, M., Long, B., Fink, T., Gafney, J., Mostman-Liwanag, H., Casper, D., 2007. Seasonal variability in otariid energetics: implications for the effects of predators on localized prey resources. Physiol. Biochem. Zool. 80 (4), 433–443.

The Three Pillars of Ecotourism

February 1, 2016/0 Comments/in Conservation, Ocean News /by aanstett

By Emily Rose Nelson, SRC Intern

Conservationists, scientists, and politicians alike are increasingly starting to understand that the natural environment can no longer be effectively managed as a separate entity from humans. We have left footprints nearly everywhere on earth and therefore, it is essential we start to factor ourselves into the equation when putting together management plans. One means of doing this, the development of ecotourism, has gained popularity in recent years. At its best, ecotourism brings people to some of nature’s most pristine areas, which then promotes conservation of wildlife and habitat, all while improving the lives of local people. At its worst, ecotourism can bring massive amounts of people to an important wildlife area, causing destruction, and completely uprooting the lives of already impoverished people. Ecotourism development, especially in developing countries, is a complicated process that requires the involvement of numerous stakeholders. Fortunately, Barnett and colleagues in fields such as fisheries science, tourism, economics, ecosystem ecology, business management, and social science have created a guide of best practices to be followed in order to create successful ecotourism in developing countries. Barnett et al. identified three main pillars of sustainability needed for ecotourism: sociocultural, environmental, and economic.

The sociocultural aspect is meant to help gain support from locals for the ecotourism project as well as identify any important social or ecological issues. This pillar needs to evaluated before anything else because without support of the locals, nothing will be affective. Bringing ideas and practices from Western society into developing countries is difficult and needs to be done carefully. Extensive research on the local culture and norms needs to be done before attempting to throw developed culture on a developing nation. For example, in the developing world fishing is often an important part of culture and considered sacred. The idea of sportfishing for pleasure, so common to our society, may be considered intrusive and rude to these people. It is also important to understand ownership and occupancy of natural resources to avoid conflicts. Finally, adapting to tourism require a whole new social and cultural norms. Locals may be resistant to this change, even if it is providing alternatives to a struggling society. It is necessary to work with the people, provide fisherman the opportunity to work as fishing guides or complement the ecotourism with public health projects to ensure they still benefit.

Boom and bust fishing cycles in the Galapagos Islands has led to the development of ecotourism, some of which as been very difficult on the locals.

The second pillar, environment, can be addressed only after the local people are on board with the plan. At this point, plans need to be set in place to manage the resources and gain the necessary scientific background on the biology and ecology of them. The basic requirement underlying ecotourism is that there is an ongoing product available to attract customers. In the case of something like sportfishing, this means the continual availability of healthy fish stocks and the conservation of their habitats. In order to ensure this, detailed studies need to be done to develop baseline knowledge of the resources that can be used for effective management. Information on fishing mortality, catch handling and post-release conditions should also be gathered and incorporated into stock assessments and best practice protocols for catch and release. When developing an ecotourism, it is critical that local people support and benefit from it. Therefore, they will have a reason to abide by conservation regulations and sustain the ecosystem. Further, if the ecotourism is able to promote the long term benefits of conservation minded practices conflicting interests that are destructive will not be given priority.
The final section, economic, should ideally only be considered after the first two are going smoothly. However, in developing nations a business plan is often implemented to the ecotourism before the necessary knowledge is acquired in efforts to generate income as quickly as possible. Unfortunately, this can have detrimental impacts if it involves threatened species or ecosystems. When done properly ecotourism can have huge economic benefits for developing nations. Locals should be given as much opportunity as possible to get involved in the business. They should be given the option of employment in the ecotourism directly filling roles such as guides or mechanics and if they are not yet equipped with the necessary skills they should be given the opportunity to learn. If not working directly for the business, they could sell local goods and services to the influx of tourists to their community. Despite these opportunities, economic development sometimes comes with unavoidable costs. In order to minimize these costs access rights should be negotiated, cultural protocols should be followed, and environmental damage should be safeguarded against.

Shark Reef Marine Reserve in Fiji is a successful example of ecotourism. Here, divers pay a fee, which is distributed to local villages that have given up their fishing rights for conservation.

By concentrating on these three pillars of sustainability it is possible to develop effective and sustainable ecotourism. Inevitably, problems will arise throughout the creation of any ecotourism plan. Therefore, it is important to realize that this is not a one size fits all plan approach, and that the guidelines described should be used and modified to fit individual situations and change as ecotourism develops. Ecotourism models should include short term coping mechanisms as well as long-term capacity building. When all of this is done, it is possible for ecotourism to provide mutual benefits to tourists, local people, and the environment.

Reference:

Barnett, A., Abrantes, KG., Baker, R., Diedrich, AS., Farr, M., Kuiboer, A., et al. (2015). Sportfisheries, conservation and sustainable livelihoods: a multidisciplinary guide to developing best practice. Fish and Fisheries, DOI: 10.1111/faf.12140.

Maltreatment as hatchlings predisposes Nazca boobies to more frequent violent episodes as adults

October 17, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By Daniela Escontrela, RJD Intern

The Galapagos Islands are home to four species of native and endemic boobies: the blue footed boobies, the masked boobies, the Nazca boobies and the red footed boobies. The name for the boobies comes from the name “bobo” which is a Spanish term for fool or clown. They are all part of the Gannet family which is also found in North America. These birds have dagger like beaks and are accustomed to diving into the ocean for their food. Although the three species of boobies nest and breed in approximately the same territories they don’t fish near each other. The blue footed boobies feed close to shore, the masked boobies farther out and the red footed boobies even farther out. The masked booby is the biggest of all the boobies; they are mostly white colored with black tail feathers and black primary feathers at the end of their wings. They have a yellow beak, with the females sporting a paler beak than the males. The term “masked” booby comes from the black skin at the base of their beak that makes it look like they are wearing a mask. Although the masked booby feeds itself by plunge diving, like the other boobies, this is rarely observed as it feeds farther offshore. These birds breed on an annual cycle, but each island has their own times for breeding. Like the other boobies, they have courtship rituals and dances but they are far less intricate than those of the blue footed boobies. The masked booby will lay two eggs but only one of them will hatch and be reared by the parents. These birds can often be found laying eggs on the islands of Espanola, San Cristobal and Genovesa. (Fitter et al 2000).

An image of a Nazca booby at Roca Union near the island of Isabela, Galapagos. Photo by Daniela Escontrela

The Nazca booby, which is native to the Galapagos, is a separate species than the masked booby but they are closely related and share a lot of the same characteristics and behaviors. Nazca boobies when young experience two types of maltreatment or violence: obligate siblicide and interactions with non-parental adult visitors. The cycle of violence hypothesis which has been tested on human subjects states that child abuse may be a cause violent behavior later in life. Nazca boobies provide a non-human model to test these hypothesis as the chicks are often subject to abuse, either from siblings or from nonfamilial adults. (Muller et al, 2011) Using the cycle of violence hypothesis, we predict that Nazca booby chicks subjected to these types of interactions may be more predisposed as adults to engage in similar aggressive activities, such as becoming non-parental adult visitors themselves. Furthermore, we predict that the predisposition of violent episodes experienced by adult Nazca boobies may be correlated with increased amounts of hormone release.

Nazca boobies vary in the size of the clutch they lay and it has been found that clutch size can often be related to the female’s food limitation (Humphries et al, 2005). The only reason the original clutch size may exceed more than one egg is because the second egg provides an insurance in case the first egg fails to hatch (Ferree et al, 2004). However, even though boobies often lay two or more eggs, usually only one of the chicks makes it to independence. The reason for this is that Nazca boobies practice a behavior termed obligate siblicide where aggression from a core chick often causes the mortality of the marginal chick which results in a brood reduction. (Humphries et al, 2005). Siblicide is often described as a form of a lethal attack coming from a sibling; if both eggs hatch, one chick will kill the other usually by pushing it off the nest. Once pushed off, the chick usually dies due to starvation, exposure or predation. Rarely does the chick make it back to the nest. (Ferree et al, 2004) In a study, very rarely did two chicks from one clutch make it to independence because of obligate siblicide. In the few cases two chicks made it to independence, one of the chicks was usually in such poor condition it almost didn’t make it. (Humphries et al, 2005)

Another form of aggression or maltreatment Nazca booby chicks experience is interactions with non-parental adult visitors (NAVs). In this interaction, adults tend to show an attraction to offspring of other parents which is often sexually or aggressively motivated. (Muller et al, 2011). There seems to be no reward for the adults that engage in this behavior while the chicks can often be injured (Grace et al, 2011). In Nazca booby communities this aggression or attraction to other nonfamilial young is common and most adult boobies engage in these acts at least once in their life. Nazca boobies are often raised as solitary nestlings (because the other chick is usually killed by obligate siblicide) in dense colonies were there are large probabilities for these NAV interactions. (Muller et al, 2011) In fact most nestlings experience NAV interactions at least once during their nesting period (Grace et al, 2011). NAV events usually occur when chicks are between 30 and 80 days old and usually happen because the chicks are left unattended while the parents go out and forage for food. When unattended by the parent, nonbreeding adults will seek the chicks for social interactions. These NAV events are less common when parents are around because the parents will chase away these adults. (Muller et al 2011)

A non-parental adult visitor (NAV) exhibits aggressive behavior (Grace et al, 2011)

There has been a positive correlation between the number of attacks chicks received (either from siblings or other adults) and the number of times the same chick participated in NAV behavior as an adult. The attacks received by the chicks at early stages of life affect and mold individual personalities. Although the siblicide behavior is a strong predictor of adult behavior, NAV events tended to contribute more to molding individual adult behavior. This shows that experiences as chicks can mold adult social behavior (Muller et al 2011).

Testosterone is a hormone released to mediate aggression. Testosterone is usually released when the argenine vasotocin system is stimulated. However, release of this hormone can be energetically expensive, especially if it has to be up-regulated for long periods of time. For this reason, according to the challenge hypothesis, testosterone is up-regulated only during social challenges. These social challenges include sibling aggression and interactions with NAVs which can be seen as times of fighting. After a study was conducted, it was found that testosterone levels tended to increase in the chicks during times of attack by NAVs or siblings. The chick being attacked tended to have higher testosterone levels than the attacker. In the case of obligate siblicide, the marginal chicks were often found to have higher levels of testosterone, even during times of no attack, because the core chicks represented such a threat. (Ferree et al, 2004) Another hormone, corticosterone which is associated with stress responses, was increased five-fold during maltreatment episodes (Grace et al, 2011).

Maltreatment behavior as adults is still not really understood. So far, three hypothesis have been proposed for the increased frequency of attacks inquired by adult Nazca boobies. One of the hypothesis predicts that “maltreatment in early life causes long term neuroendocrine changes that underline later maltreatment tendencies”. During NAV events, the hypothalamic-pituitary-adrenal (HPA) axis response is induced in the nestling under attack. Repeated activation of the HPA axis may lead to long term endocrine changes which could carry on to adulthood. These acute changes in the HPA axis experienced by chicks induced during NAV episodes, if repeated often, may increase the chances that the individual will engage in more NAV behavior as an adult. In fact, adults engaging in NAV events have been found to have higher levels of circulating corticosterone and lower testosterone levels than those adults that are non-engaged in this behavior. These difference in hormone levels may be a result of repeated maltreatment events in early life which resulted in permanent neuroendocrine modifications. The other two hypothesis that may explain increased frequency of NAV behavior as adults is that the behavior is acquired through observational learning or that it is a genetically heritable trait. However, not much evidence or research has been done to prove these hypotheses so they must be ruled out until more research is performed. (Grace et al, 2011)

Nazca booby chicks experience obligate siblicide and NAV events in the early stages of their development. These events have been found to mold individual adult behavior; as a chick is exposed to more of either of the two events, the more likely the chick is to be involved in NAV interactions as an adult. As chicks are subjected to these maltreatment events, the HPA axis is also induced, causing changes in hormone levels. This repeated activation of the HPA axis as a chick may cause long term endocrine changes that can carry on to adulthood. These endocrine changes may be the underlying factor that cause these individuals to be more predisposed to engage in NAV events as adults.

References

Ferree, E. D., Wikelski, M. C., & Anderson, D. J. (2004). Hormonal Correlates of Siblicide in Nazca Boobies. Hormones and Behavior, 46, 655-662.

Fitter, J., Fitter, D., & Hosking, D. (200). Wildlife of the Galapagos. Princeton, New Jersey: Princeton University Press.

Grace, J. K., Dean, K., Ottinger, M. A., & Anderson, D. J. (2011). Hormonal effects of maltreatment in Nazca booby nestlings: implications for the “cycle of violence”. Hormones and Behavior, 60, 78-85.

Humphries, C. A., Arevalo, D., Fischer, K. N., & Anderson, D. J. (2005). Contributions of marginal offpsring to reproductive success of Nazca booby (Sula granti) parents: tests of multiple hypothesis. Behavioral Ecology, 147, 379-390.

Muller, M. S., Porter, E. T., Grace, J. K., Awkerman, J. A., Birchler, K., Gunderson, A. R., . . . Anderson, D. (2011). Maltreated nestlings exhibit correlated maltreatment as adults: evidence of a “cycle of violence” in Nazca boobies (Sula granti). The Auk, 1-19.