showdown in nevada. it's the first contest in the west for the republican presidential hopefuls. and abc news is projecting that donald trump will finish first in the state's caucuses. can anything slow downhis campaign? and we go into the wild to the front lines of a modern war to save an ancient animal from extinction. we're with the rangers risking their lives to track poex here's horns. >> the social media secrecy that led to their daughter's murder. in this world of anonymous pricht messaging, so many parents have no idea what their kids are doing online. >> i wish i would have been there for my daughter. >> these students take us inside

first the night line five. good evening. breaking news as we come on the air. abc news can now project donald trump will be the winner in the nevada republican caucuses. based on our vote analysis, it is a two-person race for second between marco rubio and ted cruz.

victories in a row after took first prize in surlsouth carolina and new hampshire. people said they were in favor of the outsider and of those voters, 70% said they supported the billionaire businessman. we now turn to a high stakes war against trafficking. world more than gold, cocaine, even diamonds. the coveted horn of the rhino. but now a new military grade piece of machinery is being deployed in the fight against ruthless poachers. we go to the south african bush. >> in the pitch black of the south african bush, these rangers can only listen and smell for any sign that's their enemy is near. >> if they're not quiet, they will pick you up first. >> they hunt for rhino here every night. >> we need to protect them from

>> tonight our patrol has eyes in the sky. we're on the front lines of a modern war. over an ancient animal. the future of the rhino is in the balance. according to the world wildlife fun, in south africa alone, rhino poaching has skyrocketed 9,000% in just 8 years, fueled by a growing demand for its horn. ground up and used as a popular party drug in asia. more expensive than gold and some say more desirable than cocaine. with the millions made from the illegal trade, now ma nep-related and controlled by criminal networks, the plight of the rhino has global implications. in the oldest game reserve in south africa, they're trying something new. this is command central for air shepherd. a pilot project where unmanned aircraft are being deployed to help park rangers in their fight. >> nighttime operations has

for these guys. and besides meeting one the poachers you might be tracking, the danger to the animals. >> we'll just foul. you guys carry on. we'll just keep you in the frame. >> tonight's mission is about to begin and tensions are high. with ruthless poexers likely in the dark, and the reason news of a park worker mauled to death by a lion. don't let the laughter fool you. my nerves are kicking in. >> you don't know what's on the other side of the bush. the drone infrared camera picks up heat signatures of animals and humans.

to the command center. the white dots are us on patrol. the experienced rangers keep several feet between them so if one of them is attacked, they don't all go down at once. >> how many does it help? give you a sense of ease to some degree that you have this thing hovering above you now? >> i think it is quite fortunate with the drone above us. so the guys can see us. >> no signs of poachers during this patrol. but in this vast territory, the drones and patrols can only cover. so ground. in the few days we're here, four rhinos were killed. many of the rinl owes that survive these attacks are brought here to this nearby sanctuary.

somebody messed you up. somebody got paid off you, big guy. >> like this mother and her calf. >> we hear poaching all the time. look at this animal. first time i'm seeing it in my life up close and personal. but just, i mean, until you're this close to it. that is brutal. >> three months ago rescuers found her in the bush, still groggy. her horn hacked off. left for dead. her baby clinging to her side. >> is the animal still in pain? >> no. >> as much as we can get a success. >> she is healing well and soon the two will be released back into the reserve. >> man oh man. it's a shame this place is even necessary. >> it is almost unfathomable to think, what would drive someone to this kind of brutality, until you realize a single rhino horn can fetch up to a quarter

even a small fraction of that is hard to resist in a place with little opportunity. >> we're in a township outside pretty pretoria. our poacher set up a meeting for us. >> a former poacher has agreed to meet us. only if we don't show his face. >> did you ever feel bad for what you were doing for killing these animals? >> through a translator he said he felt bad but needed money to feed his family. he became a shooter and he killed at least 50 rhinos. he said his crew always had a guy on the inside. a ranger on the take. >> park officials are being off. police are being paid off. the level of corruption stretches into local government offices. given the amounts of money,

corrupted. >> most of the money is taken by criminal networks. most of it ends up here in vietnam. >> it is a status symbol for the rich. you grind it up in special designed dishes. mix it with rice wine and water. >> it is that said to cure everything. despite the ban on the trading of rhino horn, markets can still be found as seen in this bbc program. here the back of a tailor shop. a deal is underway. >> how much are you charging? >> but it's a false promise. >> there is no scientific proof that rhino horn has any benefit. >> i want to point out that it is simply made of keratin. it is exactly the same as your finger nails. >> celebrities.

never to buy rhino horn. >> even prince william took up the cause. >> together we can save our wild rhinos. when the buying stops, the killing can too. >> these slick ads may only go so far. >> you're dealing with faith. people firmly believe that rhino horn does have the attributes that it is said to have. it is the same as telling a christian, jesus christ doesn't exist. that's the level of belief that you're dealing with. for many people, it crosses beyond that. >> in africa the focus is on steming the supply. to harvesting the horns and selling them legally. >> as you know, the rhino horn grows back. it is a painless, relatively uninvasive procedure. >> i'm telling you, this is the way we will save the rhinos from extinction.

the best path forward, what we've seen here on the front lightnings are people trying everything. that's probably what it will do and more to win this battle against extinction. south africa. when we come back, the secret world of teens on social media. the digital dangers even the most tech savvy parents might not know about.front of the school. that's where your friends are. seriously, it's, it's really fine. you don't want to be seen with your dad? no, it's..no.. oh, there's tracy. what! [ horn honking ] [ forward collision warning ] bye dad! it brakes when you don't. the newly redesigned volkswagen passat. right now you can get a $1,000 presidents' day bonus on new 2015 or 2016 passat, jetta, or tiguan models. red lobster's lobsterfest is back. so come try the largest variety of lobster dishes of the year, like lobster lover's dream

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parenting has never been easy. it seal in the digital age, we have more blind spots to worry

tonight, yahoo! global news anchor katie couric takes a look at a tragedy and gives as you glimpse at the world of teens and social media. >> nicole was a very lovable person. >> tammy weeks was facing the unimaginable unimaginable. her 13-year-old daughter was found dead. >> she touched many people. >> a 13-year-old girl making headlines. >> the search for answers is just beginning. >> the reaction to her murder has become part of a conversation about girls and social media. nicole had secretly been messaging with this virginia tech student. 18-year-old david eisenhower. on the social media app kick. according to investigators, they say that one night last month, nicole snuck out of her parents' house the meet up with eisenhower and never returned home. she was missing for three days until her body was discovered 80 miles away.

determination of the cause of death is stabbing. >> nicole's story has become a cautionary tale about the dangers of secret messaging apps and their anonymous users. >> i'm willing to say kick is the devil for young children. it is like a free ability to text and parents can't see the number going in and out. >> eisenhower and an alleged female accomplice are now accused of kidnapping and murder of nicole. neither has entered a plea. nicole's father and step mother sat down with 2020. >> i wish you could have been there for my daughter. she deserved me to be there and i was not. >> nicole's family believes she turned to social media for acceptance after she was severely bullied in school. >> she had a huge boy crush kind of thing. but it was kind of innocent. she was still a child. and all she wanted was just the attention. >> we reached out to the people

have zero tolerance for any behavior that potentially affects safety of our users. we offer blocking and reporting tools to allow users to flag unwanted content. we are reviewing all aspects. >> when this case surfaced, have you heard of kik? yes. from every girl that i interviewed. >> but those secret apps are just part of the story. nancy has been reporting on youth culture for more than a decade. in her new book, american girls, social media and the secret lives of teenagers. she explores the dangers of coming of age in a world ruled by social media. >> tell me about the role this is playing in the life of the average teenage girl. >> one of the first conversations i had with some girls in los angeles really set the tone for the whole book. she said social media is destroying our lives.

it? she said then i would have no life. >> she said what she discovered was troubling. young lives playing out on various platforms that promote negative self-esteem. sometimes harsh judgment and cyber bullying. something that 13-year-old carey has experienced. >> i got a message on instagram from this guy. he seems like he was my age so i thought could i trust him. he said that he knew some of my friends. i started talking to him and we got really close. >> the friendship took a turn and carey decided they should stop communicating. soon after, she said the boy and one of his friends began writing hurtful things. >> they were saying these things like you're ugly and cursing me out when they've never met me or know me at all. it really scared me. >> her mom decided to do something about it. >> it had turned out that the person who was actually cyber

a friend of his who he was manipulating. and she had sort of taken on this crusade to get back at my daughter for no reason. i spoke to this woman. and i said your daughter is cyber bullying my child. and so she promised me it would never happen again. that she would talk to this kid's parents. and thankfully that did put an end to it. >> how has social media krebed to the notion of cyber bullying? almost every girl has been cyber bullied. they didn't necessarily call it that because it didn't lead to something. >> sale says social media has become a popularity contest. where teens seek validation from the pictures they post and the number of like they receive. she says it is having a major impact on how teenage girls view themselves.

>> i got over 150 likes. oh, you know, what a good picture i took. and then if you post a photo that you think is good as well and you don't get a the love likes, oh, my god. should i take this down? >> she said she met some girls who spend hours taking pictures of themselves and manipulating the images. we asked olivia to show us how some of these apps work. >> i can whiten my teeth. a whiter smile. if i wanted to be super blond. you can make yourself look more slender. i can make my arm thinner. what some people don't realize is that, look at the door. it's not supposed to look like that. >> but she says she tries to use these apps sparingly. >> sometimes if my voice gets really oily, i'll do that.

>> how about this depression we're hearing about among teenagers? >> think about it. if what you are thinking about is do i look hot? am i going to get liked on this photo? these the constant thoughts being raised in teenage girls' minds through their use of social media. it is not soothing. it is not something that produces a feeling of well being or security. >> both olivia and carey's moms say talking to their children about social media behavior is critically important. >> basically, your tarnlg wants to know they are part of the conversation. >> this is the way the kids will communicate. this is way life is. and you need to have the channels of communication open. you need to educate them as early as possible. as to what the dangers are. >> for "nightline, katie couric os angeles.

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sexual assault and the explosive mix of alcohol and hook-up culture creating what are some are calling fault lines. we hear from those whose allegations give us a lot to think about.

if someone has sex with you and you don't want them to have sex with you, will you stop them from doing that? the answer would have 110% been yes. then when the situation actually arose, that was not my response to it. >> "nightline" invited experts and advocates to punish state university. some who see an epidemic of sexual violence. others who feel the pendulum has swung too far accusing men. we examine consent and whether it is a vital piece of sex education that's been missing. consent on castle. a "nightline" event. thanks for watching abc news. overnight with breaking news and tune into "good morning america."

abc news.com.previously on "agent carter"... whitney frost shot my wife. i'm coming with you. no, you're going back to the hospital. i want her to pay for what she did to us. they're fake. move! move! those are fake. stop them! go! [ gun cocks ] where are the rods? jason, stop this. i know how you feel about her. daniel, don't listen to him. where?! no! wall safe at the ssr lab. he was gonna shoot you. yes, he was. so if the situation was reversed, that's what you would've done? let him shoot me? two hours ago, you were using a redacted file to frame me. if i were helping them, i'd be on my way there.

frost: the rift will open. [ gasps ] frost: zero matter will pour out, and you and i will absorb it. no! what about me?! carter: we need to close the rift. [ gasps ] dr. wilkes. whitney frost! something happened -- no! what did you do?! you're gonna pay for that. keep them alive. the key to controlling him is to control those that he loves. [ both grunt ] hello? daniel? rose? anyone? who turned out the... ...color? [ clatter ] [ gasps ] michael? come now, peggy. black and white? couldn't you have made this experience a bit more vibrant? what are you doing here? i could ask you the same question.