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Sofia Salcedo

Sofia Salcedo

Lava Lizard Expert

Nazca Boobies Offer New Insight into the Mysterious Cycle of Violence that Plagues Humans    

Water color drawing of a Nazca Booby with its characteristic orange beak.
Photo Credit: Sofia Salcedo

Forty-million innocent children know of a darkness that only they can describe (1). It is not the sweet, calm dark of night born as the sun sets, nor the darkness created by the flick of a switch. For them, it’s a darkness which lurks even when the sun shines bright. It shows no mercy and has no limits. Like molten lava, it oozes into the crevices of the battered soul taking it hostage for eternity. And when it grows tired and finally leaves it whispers, “do not tell, for my name is, “Child Abuse”.

The beautiful Española Island, Galapagos Islands overlooking a Nazca Booby colony in the distance.  
Photo Credit: Sofia Salcedo

Despite what you may think, even a place as magical as the Galapagos is not immune to such a dark facet of nature. The human eye is often easily fooled into only seeing the beauty which lies on the surface. It’s not surprising, though, since the Galapagos constitutes an archipelago of thirteen unique islands all showcasing breathtaking landscapes and incredibly diverse flora and fauna. Velvet, white beaches meet crystal clear water, overlooks reveal horizons that seem to expand infinitely, and sunrises and sunsets of the richest colors greet you every morning and night. An island covered in maroon colored dirt takes you to “Mars” on Earth, snorkeling adventures introduce you to a foreign world beneath the calm, ocean surface, and, for the first time in your life, you can approach wildlife without it scurrying quickly away. It seems as though evolution has crafted a hidden sanctuary that is simply perfect. But, this is not the case, for beneath the surface the Nazca Booby, or Sula granti, knows very well of a horrible never ending cycle - “the Cycle of Violence”.

The Nazca Booby, a sea bird common to the Galapagos Islands, is not to be confused with the Masked Booby, whom it used to be a subspecies to. Recently, scientists have agreed that beak color distinguishes the two as separate species with a yellow beak common to Masked Boobies and an orange beak common to Nazca Boobies (2). What sets the Nazca Booby apart from many other birds is its particularly aggressive behavior.

Nazca Boobies mid-fight, spreading their wings to intimidate their opponent.
Photo Credit: Sofia Salcedo

During the breeding season, a fairly large number of Nazca Boobies do not breed since there tends to be too few females to pair up with and a far greater number of available males. In other words, the adult sex ratio is unequal with a bias towards males (3). Making matters worse, after nestlings hatch parent boobies will leave their babies unattended as they forage for food (3). With unprotected nests and no nestlings of their own to supervise, Nazca Boobies, either male or female, resort to scouring the colonies for baby boobies to terrorize. This behavior has puzzled scientists for many years, but quite a few have settled on the hypothesis that “maltreatment early in life causes long-term neuroendocrine changes that underlie later maltreatment tendencies” (3).  This hypothesis is much like the age old adage, “The bullied becomes the bullier” that your elders used to tell you when you were younger and even provides a possible explanation, hormonal effects, for such behavior. A startling statistic states, “[a]bout 30% of abused and neglected children will later abuse their own children, continuing the horrible cycle of abuse”, so could it be that Nazca Booby behavior provides insight into why this is true in humans (4)? To find out scientists visited the Galapagos Islands much like I had done over my spring break.

The fifth morning aboard the lovely Frigata, our cozy yacht, was just like every other. Wake up call at 5:30 a.m., half-conscious roll out of bed into reality, and a brief, morning wake-me-up dash to the delicious Ecuadorian-style breakfast calling our names, or shall I say, stomachs?

As we inhaled the deliciousness, our knowledgeable tour leader, Fausto Rodriguez, briefed us on the day’s excursion, “Ladies and gentlemen, today we will be visiting Española Island! After breakfast suit up as quick as possible and be prepared for a dry-landing.”

Perhaps, I may have been too enthralled by the abundance of my favorite thing, food, but to my recollection, Fausto didn’t warn about the scarring encounter between a Nazca Booby adult and chick that we were yet to witness.

When our group came upon the long anticipated Nazca Booby colony situated on the edge of a rocky cliff, the land iguanas, not the boobies, were the ones having trouble remaining peaceful as they relentlessly wrestled each other. Soon enough, though, something seemed a little odd. An adult Nazca Booby started sneakily inching closer and closer to a lonesome Nazca chick as it scoured around for twigs in the process. What’s wrong with this picture is that as an effort to attract a mate, Nazca Boobies will present gifts like twigs to impress the opposite sex, yet in this case the object of this adult’s affection was a chick. Covered in scraggly gray down feathers, the chick hunkered close to the ground in fear as the adult Nazca booby stared straight into its eyes and presented the twig. Seizing the opportunity, the adult proceeded to climb atop the baby chick’s back. Although the baby was pecked at and stomped on, it simply burrowed its head into its chest and played dead rather than put up a fight. The adult became progressively more aggressive and ended the traumatic experience by raping the chick as members of the colony ignored the entire incident.

Nazca Booby exhibiting aggressive behavior on Española Island before it rapes innocent nestling.
Photo Credit: Nicholas Fletcher

Many scientists have sought to answer why such a thing happens so frequently in Nazca Booby colonies. Hormone levels, siblicide, and exposure to abuse when young are all believed to be contributors to the abusive behavior exhibited by adult Nazca Boobies (5). A study by Elisa Tarlow and colleagues examined hormone levels in visiting and non-visiting Nazca Booby adults and found that, “chick-visiting behavior may be permitted by low T (testosterone) levels and activated by, or resulting in high CORT levels” (6). Low testosterone levels are known to cause aggression and Corticosterone, or CORT for short, occurs as a result of stressful situations like attacking a nestling whose parent could return at any moment (6).  Compared to non-visiting Nazca Boobies, the T levels and CORT levels in adult visitors were different which suggest that they have a role in explaining why some adult boobies exhibit such aggressive behavior. Evolutionarily speaking, the benefit of attacking young boobies is not well known, but Tarlow suggests this behavior is so common as to “gain better nest sites through acquisition of sites where nestings die after attacks, or that non-parental avian visitors practice courtship or create future breeding opportunities by killing chicks deliberately” (6).

The tragic Nazca Booby behavior, siblicide, has also been studied to explain the aggression because of its effect on hormones.  For evolutionary advantages, Nazca boobies will lay two eggs to maximize the success of producing viable offspring, but because the eggs hatch asynchronously one sibling is slightly older and stronger by the time the second chick hatches and ultimately murders it (7). Although the practice isn’t beneficial for increasing inclusive fitness, “the impact an individual has on the survival and reproduction of relatives”, it is beneficial for its direct fitness, “the individual survival and reproduction” success (8). By killing its sibling who is fifty percent genetically similar, the surviving nestling ensures that it will have adequate food and resources to survive and reproduce and thus pass on its genes (7). According to Muller, “Siblicidal behavior ... is associated later in life with an elevated frequency of NAV behavior compared with products of 1-egg clutches and 2-egg clutches from which only 1 egg hatched [which didn’t partake in killing a sibling]”(5). Muller points to “testosterone surges experienced during sibling conflicts” as the culprit for abusive behavior later in life (5).

A baby Nazca Booby hunkers down and plays dead in order to survive an attack.
Photo Credit: Sofia Salcedo

Muller’s study also examined the hypothesis that those that are abused are more likely to do the same to others later on in life by monitoring abused Nazca nestlings through adulthood. “24 nestlings experienced 0-31 Non-parental Avian Visitor events as targets and perpetrated 1-56 events in 2004-2005” which validates that the likeliness to participate in abusive behavior as an adult increased if the adult was abused as a nestling (5).  This phenomenon may be explained by the fact that such visits are scarring to nestlings. Another scientist found that, “aggressive Non-Parental Avian Visitors, NAV, events induce a strong acute Hypothalamic-pituitary-adrenal axis stress response in nestling Nazca boobies, similar to that observed in mammals. In mammals, such responses cause permanent neuroendocrine changes”(4).  The Hypothalamic-pituitary-adrenal axis responds to stress by producing different hormones (9). These findings support the “cycle of violence” theory which many psychologists subscribe to and suggest hormonal changes as a likely reason.

Unfortunately, Nazca Booby attacks are very common and many nestlings will experience them, especially if they are left unattended like the one in this story. For a long time, scientists have suspected that those who experience abuse are more likely to abuse others in the future, yet had not gained enough supportive evidence. Nazca Boobies, however, provide a great study subject which offers insight on human behavior since abuse is very common in their life history. Clearly, abuse is a serious issue which affects people all over the world and, hopefully, with further research on Nazca Boobies we may be put an end to the ‘Cycle of Violence’ and thus save the millions of children affected by such darkness. For now, the Nazca nestling survived its share of adult Nazca Booby attacks, but will it be able to live to tell the tale when it happens again?

Works Cited:

1 - "Child Abuse Statistics & Info." Ark of Hope for Children. Ark of Hope for Children, 23 May 2015. Web. 13 May 2016.

2 - Cuccaro Diaz, Juliana, Santiago Herrera, and Ana M. Galeano. 2010. Nazca Booby (Sula granti), Neotropical Birds Online (T. S. Schulenberg, Editor). Ithaca: Cornell Lab of Ornithology; retrieved from Neotropical Birds Online:

3 - Grace, Jacquelyn, Et. al. (2011). Hormonal effects of maltreatment in Nazca booby nestling: Implications for the “cycle of violence”. Hormones and Behavior 60, 78-85.

4 - "Child Abuse in America." Child Abuse in America. Tennnyson Center for Children, n.d. Web. 13 May 2016.

5  - Muller, Martina, Et. al. (2011). Maltreated nestlings exhibit correlated maltreatment as adults: Evidence of a “Cycle of violence” in Nazca boobies (Sula Granti). The Auk 128.4, 615-619.

6 - Tarlow, Elisa et. al. (2003). Correlation between plasma steroids and chick visits by nonbreeding adult Nazca boobies. Hormones and Behavior 43, 402-407.

7 - Frostad-Thomas, Annikka. The Adaptive Significance of Siblicide in Nazca Boobies. N.p., Fall 2009. Web. 13 May 2016.

8 - "kin selection". Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2016. Web. 13 May. 2016 kin selection. (2016). In Encyclopædia Britannica. Retrieved from

9 - Alschuler, Lise, ND. "The HPA Axis." Integrative Pro. Integrative Therapeutics, 28 Feb. 2014. Web. 13 May 2016.